Fasting for Weight Loss: Does it Actually Work?

Fasting for Weight Loss: Does it Actually Work?

Fasting is probably the single cheapest and most effective weight loss tool that exists. 

It doesn't cost money to buy new foods, protein bars, protein powders or supplements and all it requires is some willpower and the ability to refrain from eating. 

But does it actually work?

Will fasting help you lose weight, trim down belly fat, and finally feel better?

My opinion is that fasting, as a therapy, can potentially help a great many people and this article is going to explain why. 

If you're interested in learning more about fasting, what it is, how it works, how it impacts your hormones, and how it impacts your metabolism then you are in the right place

Let's jump in: 


What is Fasting?

Contrary to popular belief, fasting is not when you run really really fast. 

Fasting is actually a therapeutic measure that you can take to help improve your overall health and potentially help with weight loss (1). 

And, if you aren't familiar with it, fasting is simply going without food, and sometimes water, for a set and planned period of time. 

It may sound odd, but if you think about it for a minute you'll realize that we do this naturally on a daily basis. 

Every night, before you go to bed, you eat your last meal for the day. 

As soon as you wake up you break your fast with breakfast (2). 

Usually, the length of time that you fast in the morning is fairly limited and lasts around 8-10 hours, depending on when you wake up, how much you sleep and how hungry you are. 

Therapeutic fasting works in a similar way, except this time you are planning how long you want to go without food and/or water with the hopes of reaching a pre-set goal. 

This type of therapy may sound silly but you have to realize that humans were designed to be able to handle periods without food and we do it quite well

model of how calorie restriction can lead to metabolic adaptation

Humans store fat in adipose tissue for periods when we don't have food available!

That's exactly what your fat cells are for. 

They contain massive amounts of energy in the form of calories which can be broken down in times of need. 

But why don't our metabolisms do that normally? Why do most of us continue to gain weight even when restricting our diets or exercising more? (3)

The reason for this has to do with how your hormones influence the break down of fat in your body. 

In the presence of certain hormones, your fat cells will simply not break down and they will not shrink or decrease in size. 

But, if you can influence these fat storing hormones then you may be able to finally lose weight. 

And that's exactly how fasting works:

Does Fasting Work? Fasting and Your Hormones

Fasting is so effective for weight loss because it helps normalize your fat storing hormones, it helps liberate fat stores in your body, it reduces inflammation, helps normalize your appetite and it reverses hormone resistance syndromes. 

Let's break apart each one of these into more detail. 

#1. Fasting helps normalize fat storing hormones

Studies have shown that going without food has a positive impact on insulin regulation in the body (4). 

Restricting the food you eat for 4 to 8 hour periods has been shown to help reduce body weight, improve fasting blood sugar and level out blood sugar throughout the day. 

Much of this is accomplished through the effects of insulin. 

Insulin is a fat storing hormone which is secreted in large amounts after you eat meals high in carbohydrates. 

Bread, pasta, cereal, etc. all of these foods trigger the release of insulin because your body wants to take those foods and store the calories for later use. 

This is great if you have a temporary abundance, but if you have a consistent abundance it leads to insulin resistance and chronic fat storage

#2. Fasting helps liberate fat stores in your body

In order to get in and break down your fat, you must first activate an enzyme known as hormone-sensitive lipase. 

This hormone is the rate-limiting enzyme involved in the breakdown of fat (5), otherwise known as lipolysis. 

If you don't activate this enzyme then your body will hold onto your fat cells with a lock and key. 

Hormone-sensitive lipase, as the name suggests, is sensitive to hormones!

In this case, it is sensitive to insulin levels. 

In the presence of high insulin, your body will lock up your fat cells and you won't be able to get in. 

Fasting helps to reduce insulin which triggers the activation of hormone-sensitive lipase and the breakdown of fat. 

This is exactly what you want for weight loss. 

In some cases, activation of HSL is not seen until 2 days or more of fasting, which may be why intermittent fasting does not work for everyone. 

#3. Fasting helps normalize your appetite

It doesn't make sense that fasting would regulate your appetite but let me explain how it works. 

Yes, you usually do get hungry at the beginning of your fast but this hunger eventually fades over time as your body creates ketone bodies from fat breakdown. 

These ketone bodies then circulate back and help to regulate your appetite hormones including cholecystokinin (6) (CCK) and ghrelin. 

It is well known that these hormones play an important role in regulating other hormones as well as body weight and metabolism. 

And these appetite hormones can become dysregulated with the consumption of certain foods found in the Standard American Diet. 

This can lead to a condition of chronic hunger and cravings even if you've just had a large meal! 

Fasting, as a therapy, may help to normalize these hormones which can regulate and normalize your appetite. 

#4. Fasting reverses hormone resistance syndromes

Hormone resistance syndromes, such as leptin resistance and insulin resistance, play an important role in obesity. 

Both leptin and insulin are considered 'adiposity signals' created by the body (7) and meant to reflect the total amount of fat stored at any time. 

It's the way that your fat cells can communicate with your brain. 

When there is excess fat stored in your body, your body will release higher and higher levels of leptin to tell the brain what is going on. 

Resistance syndromes are created when the body develops a resistance to these hormones at the cellular level as levels become increasingly high. 

This creates a phenomenon in which you can have high levels of both insulin and leptin which are largely ignored by the brain. 

Leptin, as a hormone, is normally secreted by fat cells and its job is to tell the brain to increase metabolism and fat burn. 

It does this by communicating with your hypothalamus as it passes through the blood-brain barrier. 

In the state of leptin resistance, the brain is resistant to the message sent by the fat cells and instead thinks that the body is in a state of starvation. 

The net result is a decrease in metabolism and an increase in hunger when you are already overweight and obese. 

This cascade of events results in weight loss resistance and can make standard diets fail. 

Both insulin and leptin resistance syndromes can be potentially reversed with fasting protocols. 

Calorie Restriction vs Fasting

Because fasting is a form of calorie restriction it's important that we spend some time talking about how fasting can impact your metabolism. 

Like calorie restriction, if fasting is prolonged for an extended period of time, it may cause more harm than good to your metabolism. 

One of the reasons that losing weight is so difficult with calorie restricted diets is because of the impact that it has on your metabolism. 

In states of prolonged calorie restriction, such as 500 - 1,000 calories diets, your body alters the number of calories that it burns in an attempt to preserve muscle mass. 

This is primarily achieved through a reduction in TRH, TSH, circulating thyroid hormones, changes in mitochondrial efficiency and energy expenditure (8) 

These changes are commonly referred to as "starvation mode" or "metabolic adaptation" and they are well studied in the medical literature (9). 

breakdown of calories burned throughout the day

As your metabolism decreases, it becomes almost impossible to keep the weight that you lost off, especially as you increase your calories back to normal. 

It is felt that this single change is responsible for the large failure of calorie restricted diets and why around 99% of people fail to lose weight and keep it off. 

So the question is:

Does fasting cause the same effect?

The answer is usually not but it certainly can. 

The goal, when fasting, is to reduce your calories in an episodic way. 

In this way, you will go through periods of feasts (normal eating) and periods of famine (fasting). 

thyroid metabolism reset poster for side bar

As long as you don't keep your calories persistently low (with too much continuous fasting) you should not trigger the 'starvation mode' or metabolic adaptation that tends to accompany calorie restriction. 

This allows you to reap all of the benefits of calorie restriction without any of the negative side effects.

How do you know if you are eating enough or if you are over fasting?

It can be difficult to tell and it may take time for you to figure it out, but as a general rule, I don't recommend fasting for more days than you are eating each and every week. 

So if you fast 4 days per week and only eat 3 days per week, you are likely putting your body in a position where you may trigger metabolic changes which will lower your metabolism

You will most likely still lose weight during your fasts, but it will most likely come back once you start eating normally again. 

Intermittent Fasting vs Prolonged Fasting

For purposes of this discussion, it's important that we distinguish between intermittent fasting and prolonged fasting. 

There aren't any strict definitions between the two, but I've gone ahead and created some guidelines to help you below:

  • Intermittent fasting = Intervals of going without food for 18 hours or less. 
  • Prolonged fasting = Intervals of going without food for 18 hours or longer. 

Intermittent fasting protocols can absolutely be helpful for weight loss and balancing hormones, but they are not nearly as powerful as prolonged fasts. 

Intermittent fasts usually last no more than 18 hours and can be done several times throughout the week. 

A sample intermittent fasting schedule may look something like this:

  • #1. Monday/Wednesday/Friday - Stop eating at 7pm, start eating at 11am the following morning (14 hour fast 3 days per week)
  • #2. Tuesday/Thursday - Eat only between the hours of Noon to 6pm (18 hour fast 2 days per week)
  • #3. Saturday/Sunday - Eat a total of 500 calories per day on both days and a normal amount of calories Monday-Friday

This type of fasting is certainly helpful (and better than nothing) but would not be as powerful as fasting for longer periods of time. 

It seems that fasting as a compounding benefit the longer you fast. 


All the hours you spend fasting are not equally beneficial to your body. 

Hours 1 through 10 may help you burn through glycogen in your liver, while hours 10 through 14 may be where all of the positive benefits occur. 

So, in a way, you are fasting in the beginning only to reap the benefits achieved later in the fast. 

Hopefully, this is making sense!

And that is why prolonged fasting tends to provide superior results when compared to intermittent fasting. 

You spend a longer amount of time in a calorie restricted state where your body can benefit from the hormonal changes which occur. 

Intermittent fasting can still be beneficial, and a great stepping stone into prolonged fasting, but it may not be enough for serious weight loss in all people. 

Is Fasting Dangerous?

For some reason, many people like to look at fasting as some sort of dangerous therapy that may have adverse consequences. 

But, when we look at fasting in a logical way, it's easy to see how many of these critiques could be interpreted as fear-mongering. 

And, clinical studies tend to confirm that fasting can be a completely safe and effective weight loss tool (10). 

After all, do you think it was possible for our ancestors (on the desert plains) to have access to food 24/7?

Were they walking around with cold drinks, refrigerated 100 calories or easy access to the dollar menu at fast food restaurants? 

The answer is obviously no. 

In fact, we have evolved to be able to handle prolonged periods of time without food and still work quite well. 

In addition, fasting can actually enhance certain functions in your body. 

Consider this example:

If you were a pre-historic caveman or cavewoman, would it make sense for your body to completely shut down after a few hours without food? What about 12 hours? What about 32 hours?

If you have gone 32 hours without food doesn't it make sense that your body would trigger changes in your physiology to help you become more clear, more alert and more capable of finding food?

After all, your survival depends on it. 

Well, this is exactly what we see happen in people who begin fasting. 

They experience all of the benefits (and others) that I've just described here. 

And studies have shown that fasting can affect your body in the following ways (11):

  • Increased anger
  • Improved pre-frontal-cortex-related cognitive functions
  • Increased mental flexibility
  • Higher parasympathetic activity
  • Decreased frontal brain activity

But what about safety?

One of the first questions that people have about fasting is whether or not it is safe. 

To answer this question let me give you some important examples:

#1. David Blaine fasted for over 40 days (12). 

#2. The longest fast recorded was 382 days in a 27-year-old male (13). 

#3. 34-year-old male who underwent a voluntary 50-day fast (14). 

Both of these individuals were healthy and safe after their fasts, experienced significant weight loss, improvements in cholesterol levels and so on. 

And, when I talk about fasting here I'm not talking about several day-long fasts. 

I'm talking about going a set amount of time, ranging from 16-24 hours, without food. 

But, if we are being fair, just because fasting was safe for those individuals doesn't mean it is necessarily safe for you. 

risk factors for fasting in certain individuals

Most of the safety issues surrounding fasting have to do with the concurrent use of medications, especially medications designed to lower your blood sugar. 

As you fast, your blood sugar may drop, and this drop may be exaggerated if you are taking glucose lowering medications like insulin or other anti-diabetic medications. 

The good news is that the presence of these conditions doesn't preclude you from being able to fast. 

But it does mean that you should be diligent when fasting and make sure you monitor your blood sugar closely and adjust your medications appropriately. 

Many religions employ the use of fasting and for years patients have been following these guidelines (15) even though they have medical conditions such as type I or type II diabetes. 

Studies have shown that it is safe to fast for extended periods of time provided you adjust your medication appropriately. 

Other people, when they start fasting, may experience mild side effects including headaches, dizziness, hunger pangs and changes to their body temperature. 

Most of these mild side effects tend to fade over time as your body adapts to the fasting process and are not necessarily things to be worried about. 

In some cases, sudden changes to insulin levels may precipitate the release of electrolytes such as potassium and sodium (16). 

You can replace these nutrients with an electrolyte drink or by using salt water during your fast. 

Water Fasting vs Dry Fasting

There are many different ways that you can do your fast including:

  • Fat fasting - Eating only fat during your fast for some length of time
  • Water fasting - Consuming only water during your fast
  • Dry fasting - Consuming neither food nor water during your fast
  • Fasting mimicking diet (17)
  • And other variations

Each of these types of fasts has their own benefits and they are important to discuss because if you can't do one then you might be able to do the other. 

Water fasting is probably the easiest and safest way to get into fasting. 

If you are water fasting, then during your fast you can consume as much water as you want. 

This is beneficial because it reduces the risk and symptoms of dehydration, it can help you feel full and is probably safer for older individuals. 

One potential downside to water fasting is that it may not be quite as beneficial (in terms of the impact it has on the body and your hormones) when compared to dry fasting. 

Dry fasting is when you go without both food or drink and you prevent putting anything inside of your mouth for an extended period of time. 

Dry fasting can last for as few as 12 hours but go beyond 24 hours in some cases. 

Dry fasting is said to be more powerful than water fasting because it puts more stress on your body as it has to deal with both a lack of food and water

If you choose to do dry fasting then you need to be in a position where you have water available to you and it's probably a good idea to have a friend or someone else around in your house just in case!

It's not as dangerous as it sounds, but the older you are, and the more medications you take, the more likely you are to experience some side effects. 

I've personally done both water fasting and dry fasting for up to 48 hours at a time. 

I find that dry fasting definitely requires more willpower and tends to "sap" my energy more than water fasting, but I find it to be far more effective (at least for me). 

Fat fasting or fasting mimicking diets are ways that you can consume 'hormone neutral' foods during your fast. 

The idea here is that you can consume certain types of foods which contain only fat because these foods don't influence your insulin or leptin levels. 

Fat fasting is not quite as potent when compared to other forms of fasting but it's an easy way to get your feet wet. 


Fasting is a therapy that can be used to help obtain weight loss and it can even be safely combined with other therapies such as medications, supplements, diet, and exercise regimens. 

As a therapy, it's also incredibly cheap and perhaps one of the most effective weight loss therapies that you can use. 

The benefits of fasting seem to come from its effects on certain hormones including insulin and leptin. 

These hormones help to regulate body weight, fat storage, appetite and your metabolism. 

Fasting is generally safe provided that you don't have any co-existing medical conditions or take blood sugar lowering medications. 

There are many different types of fasting including prolonged fasting, intermittent fasting, and variations of each. 

Be cautious when fasting, however, because extended periods of fasts can still potentially damage your metabolism. 

Now I want to hear from you:

Are you currently using a fasting program?

Is it working for you?

Have you lost weight? 

Why or why not?

Leave your comments or questions below! 

References (Click to Expand)

is fasting the best way to lose weight?

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 70,000+ people have used them over the last 6 years. You can read more about my own personal health journey and why I am so passionate about what I do here.

41 thoughts on “Fasting for Weight Loss: Does it Actually Work?”

    • Hi Laura,

      I think that’s another myth that’s been potentiated through the grapevine. I’ve used it on a great many people with adrenal problems without any issue. You just have to do it cautiously. If you jump into a long fast then you probably won’t do well, but if you ease into it then you shouldn’t have an issue.

  1. Great info Dr. Childs, thank you. I’ve read that women respond differently to fasting than men, and that fasting can cause unhealthy shifts in estrogen and other hormones in women. Do you recommend a 1x week 14-24 hr water or dry fast with intermittent fasting the remaining 6 days? I’ve been doing intermittent fasting and feel good, but was concerned about negative impacts on hormone levels since I am already dealing with thyroid issues.

    • Hi Lisa,

      I think it’s largely a myth that women don’t do well with fasting. Anyone can do poorly with fasting if it’s done incorrectly, and anyone can do amazing if it’s done correctly. There are very few cases where it is absolutely contraindicated.

  2. When you are done fasting for a given period of time, are there certain foods to start eating and what should your caloric intact be for the day? I am currently on a low carb diet.

    • Hi Gwen,

      Not really, just make sure to consume healthy foods afterward. You’ll want to match your calorie intake to your basal metabolic rate.

  3. I’m currently doing your weight loss program with 2, 24 hour consecutive fasts… I think I know the answer to this, but can you do the first day fast for 28 hours, for example, and then the second day fast for 20 hours?

    • Hi Meghan,

      That probably won’t be an issue, but you’ll have to play around with it to make sure that it’s working for your body.

  4. Hi Dr Childs,
    Thank you for this information.
    I started doing intermittent fasting at the beginning of 2018, and went down to 1 meal a day.
    Then I did three extended fasts in a 5 month period. They were long fasts, the first one was 14 days, the second one was 19 days, and the third one was 9 days.

    I am not overweight, I weighed around 60 kg for 1.64m at the beginning of each fast. I was doing it more for the autophagy aspect of the fast, and also a little bit for the weight loss.
    I felt very tired during the first 2 fasts, very weak. I drank only water coffee and tea the first fast, then only water the second fast, and the third fast I drank water and took a multimineral and multivitamin plus chlorella and wheatgrass juice powder. I felt less sick and tired during the third fast.

    At the end of the first and second fast, when I started refeeding I became really swollen, I retained a lot of water after the second and third day of refeeding, it was hurtful on my skin at waist level and legs. It took more than 2 weeksfor the edema to go away. The first and second fasts I broke with carbohydrates, fruits prominently, and some fat during the first couple of days before going back to eating normally. The third fast I broke it with only fat and veggies, and was able to diminish greatly the edema that usually follows after breaking the fast for me.
    I finished my third fast 33 days ago.

    I did these extended fasts because I wanted my body to heal my thyroid, which has been hypo for many years.
    I am not sure if it changed anything, I have not done lab tests to see if it improved something, but I have noticed my hair falls a bit less and I am not cold during the French gloomy winter nights, when before, I had to put a hot water bag on my feet just to be able to warm up a bit faster and stop shivering.

    What I learned from this experience related to your article is that doing long fasts is definitely harmful for the metabolism, at least in my case, because now, I feel that my appetite is always high, I feel like eating all the time and need a lot of will power to restrain myself from eating even when I’m satisfied. And I tend to eat a lot more now than I did before I started fasting. I even ended weighing 4 kg more than what I weighed before the fasts. I am now 61kg, I was 57 kg. And this weight gain pattern happened following all three fasts.

    I am now trying to heal my metabolism and regulate my appetite. There are days when the brain signaling is so powerful that I cave in and binge all day. Some other days I am able to eat “normally”. I do not eat junk food, just too much of good food like fruit, nuts, eggs and, well, some say it’s not good some say it is: organic dairy. I eat everything organic that’s for sure.

    I do HIIT 5 times a week to up my metabolism, and have bought a ton of supplements to help me with my thyroid and to boost my metabolism (green tea extract, bitter orange, st johns wort, garcinia, chromium, banaba leaf, copper, guggul; Iodine, zinc, selenium, l-tyrosine, ashwagandha, holy basil, licorice, and maca, the list is long). I take fulvic humic acid every day and a multivitamin.

    Currently I’m just trying really hard not to gain any more weight, because even doing a 24 hour fast is too much for me (psychologically). So I take chitosan hoping it will nullify some of the harm (provided it actually works) when I overeat.

    I recently learned (3 weeks ago) that doing more than 2 days water fast is detrimental for the body because of the extreme level of toxicity we all have in our bodies, and maybe that is why I felt so weak during my fasts.

    I have been researching the niacin + infrared sauna detox. According to my readings it could be a good alternative to detoxing by water fasting.

    My ultimate goal is and always has been to heal my thyroid, because that is the cause of my excess weight and tendency to gain it very easily. I first was able to treat some of the symptoms and lose weight 3 years ago by doing a homeopathic therapy (I have never taken any allopathic medicine, not even for the flu). I lost 20 kg in a 2 year period: slowly but steadily. But this year I wanted to actually heal it (therefore the long fasts for autophagy).

    I hope I didn’t hurt it more than I helped it. And I really hope I did not regress by doing these fasts and that my metabolism and appetite will come back to what they were one day soon.

    Could you give me a piece of advise please?
    What is your opinion on the infrared sauna + niacin detox? I would love to read your thoughts on this.

    Thank you!

    • Hi Jepsiba,

      It definitely sounds as if you have damaged your metabolism as a result of over fasting. Excessive fasting is really just excessive calorie restriction and causes the same issues that pretty much any calorie-restricted diet does. I think fasting can be good, but if you undertake it without proper supervision you risk causing more harm than good. I am actually beginning to see this more and more as a result of more people fasting, especially with existing thyroid problems. You can learn more about how it impacts your metabolism and potential treatment options here:

  5. Hi Dr Childs,

    Thank you for the great info. I am planning to start intermittent fasting but am unsure how to begin. Do I stay in my caloric maintainance, if so wouldn’t my body have the need to breakdown fat since it has enough energy during fasting? Or should I restrict calories to -500, would that damage my metabolism?

    I lost almost 50lbs from calorie restriction and beach body programs, but after a year I have gained all the weight back. I have been trying to exercise and reduce calories again but I have been an a plateau for two months now. From what I have read, I think I might have damaged my metabolism form excessive dieting. (My tdee is 2000 and for 3 months I restricted my calories to 1400)

    Is there a way to fix my metabolism thru fasting? Thank you hope you could help.



  6. Hi – what are your thoughts on water fasting or intermittent fasting while breastfeeding? Is it safe? Will toxins be eliminated through the milk granted you are able to sustain a good milk supply?

    • Hi Anne,

      In general, it’s usually an okay thing to do if you are breastfeeding but you should proceed with caution because it may cause your supply to dry up. I only ever recommend it on a case by case basis.

  7. Hi Dr.Childs,

    I was diagnosed with Hashimoto’s early Jan 2019. Im 28 years old, weigh 164, 5’9”. Gluten-free diet for 10 years, dairy free, organic/non-gmo, grass fed.. etc. Used to be insanely active (swimmer, dancer, active 2x per day, etc). Recently, I dont have the energy and have resorted to IF + Keto + CICO. Since college, I have slowly put on 10 pounds that im desperate to lose. Will IF and strict Kept hurt Hashimoto’s? I’m on 30mg of Amrour and have noticed zero weight loss benefits. I wish you were taking clients!! Any advice is so appreciated, thank you!!

  8. I did a 48hr dry fast a few weeks ago and it was amazing! I want to make it something I do every 6 months.
    When dry fasting, how do you take your thyroid meds?

  9. After reading your site dealing with SIBO and fasting with thyroid I started fasting in mid-January. At Christmas time this past year, I got into food allergies and was diagnosed with hypothyroid. I believe I have SIBO but have never been diagnosed although my doctor is perplexed with my body’s lack of absorbing nutrients. I eat lunch one day and breakfast and supper the next day drinking water whenever I need to feel hydrated. I have lost 25 pounds and on occasion am still dealing with temperature swings in the body. How long do you recommend fasting? I am in my early 40’s presently sitting weight at 224 lbs at 5’8.5″. I found with the fasting and medication I have more energy than I did prior to starting the fasting.

    • Hi Jean,

      The short answer is that it’s different for each person. You want to be careful not to over fast or you risk damaging your thyroid and your metabolism. I usually make that call based on a number of factors and it’s different for each individual.

  10. Is this information correct or a typo? increased anger???

    And studies have shown that fasting can affect your body in the following ways (11):

    Increased anger
    Improved pre-frontal-cortex-related cognitive functions
    Increased mental flexibility
    Higher parasympathetic activity
    Decreased frontal brain activity

    • Hi Lisa,

      The information is definitely correct and not a typo. Fasting can increase anger as an emotion in those who do it. I’m sure you are familiar with people who get “hangry” when they are hungry. You can read the study listed there for more information.

  11. Hi, I have been reading so much of your articles. I am 54 I have hypothyroidism/hashimoto. Had a hysterectomy because of issues with fibroids and bleeding. Have only 1 ovary. Was on estrogen therapy, but off it now because I had surgery. I have high BP, which is under control with meds. Taking cholesterol meds for high cholesterol. Taking Tirosint for hypothyroidism. Can’t lose weight. Currently trying to do ketogenic diet, which isn’t working. Have serious issues with bloating/ gas/constipation. I don’t sleep well. Very low energy. I do a traditional endocrinologist. My weight has gone up gradually. Totally out of my control which stresses me out. I don’t know what to do.

  12. I have read several expert opinions that fasting should be done differently in women than in men due to women having a more “trigger sensitive” famine response. Do you agree? If yes, what recommendations do you have for women?

    • Hi Lisa,

      I try to tailor fasting protocols to the individual more than the gender. If you try a one-size-fits-all approach then I could see you running into issues, but that’s never been the case with the individual first approach.

  13. Hi Dr. Childs,

    I have your whole weight loss program. I’m a doctor, and I have a doctor that does all the labs and rx I want. I have done the hcg diet about 3x a year for more than a few years. I was beginning to realize that it was having a negative affect b/c I would always regain the weight as soon as I tried incorporating any starches. I have all my needed labs and I have leptin 50, insulin 11, thyroids were all low “normal”, but really just low. I’m pretty sure my adrenals have been quite stressed and I have been supporting those with herbal adaptogens for quite a while. My hormones are all quite low but we have not really addressed those yet. My energy has been really low for years. 2 months ago when I bought your weight loss program I figured out what I wanted and went into my doc. I’m now taking T3 and LDN and frankly my energy is about 1000% better. I found out I have chronic fatigue, but I’ve been able to get a handle on that very quickly thanks to my own research. I started doing your program and lost about 7lbs in the initial weeks with the fasting +hcg. But after that I noticed a regain of about 3lbs and the fasting 2x week wasn’t having any change on my weight. I’ve stopped the fasting for now and since gained back the rest of the 7lbs I’ve lost. I’m also doing ALA, berberine, myoinositol, Oralvisc, adrenal adaptogens, mitochondrial support supplement. My other issue that my doctor is making strong suggestions is I eat pretty low calories, around 1300 per day. I’m just full after that amount. I have forced myself to get up to 1600 or so, esp when I had the energy for working out, but if I just eat when hungry and stop when full it’s about 1200-1300. I’m thinking I can’t expect any weight loss for 6-12 months in order to fix things. Do you recommend restarting the 2x fasting a week at this time or would you suggest waiting? Should I force myself to eat more calories? It feels likes bordering on disordered eating when I’m constantly worried about eating enough, which also makes the fasting days difficult b/c if I feel hungry my knee jerk thought is I have to go eat. Then I have to remind myself that I’m fasting. The fasting days have been slightly difficult because of that. Thanks for any answers you can give.

    • Hi Michel,

      Based on this information, it does seem that you have a fairly damaged metabolism and I suspect that it will take quite a while for this to recover completely (probably several years). I do think, because of that, it’s a good idea to hold back on the fasting for now (probably for several months) and focus on your thyroid/adrenals. The information will still be relevant to you, but you probably don’t want to get too intense with it for several months until your body is in a weight loss receptive capacity.

  14. Hi Dr. Childs,
    Despite living an active lifestyle, I have struggled with my weight since childhood (now 23). I was recently diagnosed with Hashimotos as well as PCOS and mild insulin resistance/high blood insulin levels. I have been prescribed Thyroxine which I’ve been taking for a few weeks now. I’m very interested in trying intermittent fasting, but am still trying to figure out which method works for me. I’m an RN and work on a very busy critical care unit, so I don’t feel that fasting during my 12 hour shifts is a good idea due to the stamina required. Also, I work night shift 3-4 nights per week and sleep during the day. But on my days off, I switch back to sleeping at night. So I’m struggling to decide when the best time is to take my thyroxine. Any advice you may have in these areas would be greatly appreciated!

    • Hi Anonymous,

      I would caution against working nights long-term. It’s been shown studies that working nights has a negative impact on hormone balance including reduced growth hormone levels. If you have the hormone imbalances described here you would want to make sure that you are sleeping enough and not overstressing your body as both of those things can worsen PCOS and insulin resistance. When you take your thyroid medication probably doesn’t matter so much as long as you stay consistent with the time of day that you choose.

  15. Hi, Dr. Childs –

    Thank you for all the information on your website. I almost certainly have insulin resistance (Hg A1C = 6.9), and anti-thyroid antibodies with TSH within normal limits. I recently tried intermittent fasting and felt absolutely horrible – hungry, dizzy, and weak – when I tried to work out. Worse, I wake hungry many nights and can’t get back to sleep without at least a small amount of carbs – a piece of buttered toast, for example. I’m unable to lose weight despite working out with a trainer for 8 months now. Any suggestions for how to get started to fix this metabolic mess?

  16. 47 years old with Hashimotos, Lipedema and mild congenital lymphedema currently taking 2 grain NDT. Gastric sleeve 6 years ago. Highest weight400. Lowest after surgery 230.

    I have experienced a lot of regain after bariatric surgery. Up to 292. My dr gave me Phentermine and told me to take a pill a day. Told him I wanted to experiment with taking less and taking it intermittently. He says fine as long as not more than a pill a day.

    I have been using phentermine to help manage fasting days and so far it has been going really well. I take the 9ish mg (quarter pill) on two days a week and water fast 9 pm until afternoon (around 1 or 2) I eat a normal lunch and a normal dinner.

    Two days a week I take 18ish mg. On these days I eat at 8 pm, wake up at 5:30 take my NDT and phentermine drink 16 oz water but no food. Then no more food or water until 8 pm when I break my fast.

    The other three days of the week I don’t take the Phentermine and I just eat a normal diet (around 2,000 to 3,000 calories)

    I am pretty active working in retail 45 to 50 hours a week.

    I have lost 12 pounds the first month down to 280. Which is like a miracle that I cannot even accomplish on a 900 calorie VLCD! Even after VSG the most I ever lost in a month was 9 pounds. I know a good portion of it is lymphedema fluid so not all fat obviously but I feel really good following this schedule and the fluid buildup is just as unwelcome as the excess fat.

    Just wanted to share my experience. Any feedback or advice is always welcome.

  17. Hi Dr. Childs-

    Is it safe for me to do a 3-5 day water fast if I’ve had my thyroid removed? How will it affect my TSH, T4, T3 levels? I hear it will stop my medications from working properly. Thanks

    • Hi Alycia,

      It will impact how your body metabolizes those medications and should be done under some sort of supervision just to be safe.

  18. Hi,
    I have hypothyroidism and pcos. I had a hysterectomy at the age of 26 due to heavy periods which I’m suspecting were due ro my thyroid , also history of infertility in the past. After the birth of my daughter I lost a lot of weight without trying in a very short period which I also suspect was thyroid related possibly brought on by pregnancy hormones.
    Anyway I’m now 51 and up to a month ago I was piling weight on , had sugar cravings which sisnt help with my weight. I live in the uk and levothyroxine is the only thyroid supplement available in the NHS you can do private but even so they are reluctant to prescribe natural thyroxine, therefore doe the past 6 years I’ve been self medicating with thyroid s and have felt much better up to the last month when my weight was creeping up, feeling cold, no libido at all. I gathered my thyroid is to blame so I ordered some saxenda online and am now on the third week and have found I’m doing much better especially incorporating the 18:6 program of eating with it, because my thyroid is functioning low I have 900 to 1000 calories a day and I have so far lost 15 lbs in this period. I suspect I have insulin resistance and have been monitoring my blood sugars twice a day my waking reading is on average 5.5 mmols and my evening one is 5 mmols on average bearing in mind my morning reading is 10 hrs without food. I have lost 5 inches from my stomach which is amazing I feel amazing plus I have spinal stenosis and DDD and my pain levels have gone from 10/10 to 2/10 so I’m thinking my inflammatory markers are also reduced.
    The reason I am contacting you is I sont want to damage my metabolism. Thankfully as a RN I can order my own bloods my last tsh showed hypo . But again the uk is behind with how it manages thyroid issues and relays solely on tsh I however order t3 and t4 which I remember they were within the normal range, cant remember the exact figures but something was going on I just felt foggy headed and not myself
    So you think it’s possible now I’m following IF my insulin is being used correctly and I’m not using fat stores instead of laying them down? I am happy with this plan and it suits me, I’m also no longer craving sugar.
    Am I sound the right thing? Like weight loss is great , having no pain is great sleeping better is great but is it great to follow IF forever as my way of eating obviously slowly increasing my calories once I hit target? I have 35 more lbs to lose to be at my ideal weight so still a dairy way to go. Would just like some reassurance I’m on the right track. I feel like doctors over here dont listen so I’m having to so this alone. Thank you so much .

  19. I have that typical bulging hypo stomach despite only weighing 100lbs and have suffered what feels like blood sugar issues/IR since my teens and before going on Levo, as well as recent high cortisol symptoms. I’ve even had to cut out coffee. It’s hard to say which came first- IR or hypo. I understand this is most likely a low total T3 and FT3 issue for me but can fasting help reduce that belly and IR and as a result help the T4/T3 conversion. I”m highly suspicious that insulin resistance could be affecting T4/T3 conversion.

  20. I have been IF since 11/21. I follow an 8/16 plan. I eat healthy from noon to 8pm. Noticed that most of my overeating was in the evening. I am down 18 lbs so far, can’t believe how good I feel. I have a cup of green tea for breakfast which keeps me going until noon. I thought it would be harder, but I truly find it very easy. I do take my vitamins Thyroid Daily Essential faithfully. Just turned 70, I work full time and feel great.


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