What Really Makes Thyroid Patients Get Fat?

What Really Makes Thyroid Patients Get Fat?

Thyroid problems lead to weight gain but probably not in the way you think they do. 

Let me ask you this: 

Does it make sense that people suddenly start eating more and exercising less when they get their thyroid diagnosis?

And it’s this sudden behavior change that’s responsible for the weight gain that 80% of thyroid patients deal with (1)? 

Or do you think it’s more likely that there’s something else causing this weight gain that’s related to the function of the thyroid itself?

It’s definitely the latter and that’s exactly what I want to talk about today: 

What really makes thyroid patients get fat…

Because if you can understand this then you’re already well on your way to getting and staying lean. 


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#1. Not Eating For Your Thyroid

The best diet is one that helps you stay at a normal weight. 

And because thyroid function is connected to your weight, we also know that the best diet is one that optimizes your thyroid. 

The problem is, most thyroid patients aren’t eating with their thyroid in mind, they are eating primarily for weight loss. 

But some of the “best” weight loss diets are also the worst for your thyroid

I’m not saying there’s a specific diet that works best for all thyroid patients. 

But there are definitely some guidelines that all thyroid patients should follow if they want to eat to improve their thyroid. 

This includes both things you should be eating and things you should be avoiding. 

Let’s start with what you should be avoiding first. 

Here’s a list of habits that have the potential to make your thyroid worse and lead to weight gain: 

  1. Chronic daily calorie restriction – this would be something like cutting your calories to 1,000 calories per day for 30-60 days in a row. This form of calorie restriction slows down your thyroid and should be avoided. If you need to reduce your calories then fast. 
  2. Long-term low carbohydrate-based dietsyour thyroid needs carbohydrates to function and cutting them out for long periods of time can lower T3 and increase TSH. If you want to cut carbs then carb cycle or go low carb for short periods of time. 
  3. Eating ultra-processed foods – This one is self-explanatory. Processed foods are inflammatory and calorically dense. The more you eat, the fatter you’ll get. 
  4. Drinking too much coffee and other sources of caffeine – These drinks are often used as a crutch for energy to fight fatigue but usually just make fatigue worse in the long run. 
  5. Overeating – Thyroid dysfunction impacts your cravings and reduces willpower. If you don’t pay attention to this, you can easily eat more than you need. 
  6. Avoiding vegetables – Yes, vegetables do contain goitrogens but, no, they will not make your thyroid worse. Boil or steam them and this problem is pretty much solved. 
  7. Using artificial sweeteners – These sweeteners may cause Hashimoto’s and their use tracks with other chronic health conditions including weight gain

And here’s a list of some habits that will help your thyroid function better and help you get leaner: 

  1. Eat at least 100 grams of whole-food carbohydrates each day
  2. Consume at least 100 grams of protein each day 
  3. Do not restrict your calories unless you are fasting
  4. Eat fish at least twice per week 
  5. If using cooking oil, opt for extra virgin olive oil but try to get most of your fat from whole foods

What’s frustrating is that this may seem overly restrictive, but you can’t compare your needs to those of someone without a thyroid problem. 

The reality is, that you’re just going to have to be more cautious and careful about what you put into your body because of your condition. 

But if you eat to optimize your thyroid and throw in diet and exercise, you’ll find fat melts off your body. 

#2. Taking The Wrong Type Of Thyroid Hormone

Thyroid hormones are not all created equal. Some are just far more powerful than others. 

It just so happens that most thyroid patients are taking the absolute weakest form of thyroid hormone known as T4. 

T4 is found in the most commonly prescribed thyroid medications like levothyroxine and Synthroid. 

Doctors use this form on purpose because they believe it’s superior and more stable. 

While it’s definitely more stable, it’s far weaker and often keeps thyroid patients fat. 

In fact, there’s evidence to suggest that levothyroxine use may be associated with weight gain both from studies (2) and patient experience.

On the other hand, T3 does the exact opposite. 

As a thyroid hormone, T3 is hundreds of times more biologically active compared to T4 and does not require activation. 

Which is probably why studies like this show that swapping out T4 for T3 results in weight loss and better cholesterol management (3). 

shop thyroid supplements for all thyroid patients

In this study, patients were randomized and given either T4 or T3 in equivalent doses. 

Compared to those taking T4, patients taking T3 saw a decline in their weight by 5 pounds over 6 weeks without making any other changes to their lifestyle. 

T3 does a much better job of improving metabolism because it’s a stronger thyroid hormone. 

And if you can improve your metabolism by even an extra 25 or 50 calories per day, you will effortlessly lose weight over time. 

This study only went on for 6 weeks, but it’s possible that these patients would have seen even greater weight loss had they continued for 6-12 months. 

Bottom line? If you aren’t losing weight on levothyroxine, try switching to T3. 

T3 can be found in thyroid medications like Cytomel, liothyronine, and Armour Thyroid

#3. Insulin Resistance & Leptin Resistance

Yes, calories are an important part of weight management, but so are your hormones. 

And for thyroid patients, hormones are often much more important. 

Two in particular stand out: 

Leptin and insulin. 

Both of these hormones send messages to your brain that then get transmitted to your thyroid. 

When insulin and leptin are high, your body knows that it needs to increase thyroid hormone to help burn off that extra energy. 

That’s how it’s supposed to work. 

But the dysfunctional thyroid state often leads to resistance in these hormones known as leptin resistance and insulin resistance. 

In states of insulin resistance, the body has a difficult time breaking down fat cells for energy use. 

This obviously makes it difficult to lose fat if you can’t burn it for energy. 

Leptin resistance does something similar but through a different mechanism. 

Normally, leptin gets secreted by fat cells which impact the hypothalamus. 

This activation leads to an increase in TRH, TSH, and, finally, T4 and T3. 

If leptin falls, or if you are resistant to the effects of leptin, this signal doesn’t get communicated and thyroid hormone levels will fall (4). 

Less thyroid hormone means a slower metabolism which leads to weight gain. 

Both of these conditions are common in thyroid patients, both conditions lead to weight gain, and both conditions are missed by most doctors. 

How can you tell if you have them? 

With a couple of simple tests. 

You can check your fasting serum leptin and, if it’s elevated, and you are overweight, and unable to lose weight, you have leptin resistance. 

Insulin resistance can be diagnosed by testing your fasting insulin, blood sugar, and Hgb a1c. 

If either of these conditions is present, they MUST be reversed if you want to lose weight regardless of what you do with your thyroid. 

#4. A Lackluster Lifestyle

This one applies to everyone, not just thyroid patients, but thyroid patients are more sensitive to a bad lifestyle than a healthy person. 

This means you’ll need to be more vigilant about how you treat your body. 

You won’t be able to get away with cheating on your diet, or cutting out an extra hour of sleep, or not exercising because you’re too tired. 

This is just the reality of your situation. 

But the good news is that all of these things are modifiable and all of them are completely under your control. 

And, even better, optimizing your lifestyle will make your body less reliant on thyroid medication. 

The big killers of your thyroid and the main causes of weight gain include: 

  1. Not getting enough sleep – you should aim for 8 hours per night.
  2. Too much stress – If you can’t get rid of stress then take adrenal support supplements.
  3. A poor diet – We’ve already discussed this one so refer back to our previous discussion if you need to. 
  4. Relying on coffee and caffeine for energy – while they may make you feel good temporarily they often reduce sleep quality. 
  5. No exercise – don’t exercise just for calories, exercise because it helps your thyroid.

Whatever you do, don’t think you’re going to be able to lose weight by ignoring these things. 

No matter how strong your thyroid medication is, it won’t make up for a poor lifestyle, and, avoiding this, is one quick way to stay overweight for a loooong time. 

#5. Not Enough Lean Muscle Mass

Want to know what separates people who are able to lose weight and keep it off versus people who just regain that lost weight right back? 

Lean muscle mass. 

Not only does lean muscle mass improve your metabolism, it’s also a huge target for thyroid hormone action

A lack of lean muscle means less thyroid function overall. 

But, wait a minute, don’t overweight people have tons of muscle because they have to carry around all of that extra weight? 

Yes, but the quality of that muscle mass is poor (5). 

As a thyroid patient who wants to get and stay lean, your goal should be to preserve muscle mass but also ensure it’s of high quality. 

The key to quality muscle is exercise and the key to muscle mass volume is your diet. 

This is why you can’t skip out on lifestyle changes like diet and exercise. 

You don’t need to exercise to burn calories, you need to exercise to improve the function and size of your lean muscle mass.

#6. It’s Not Actually Fat (It’s Water)

There’s also another cause of weight gain that thyroid patients have to deal with and that’s water weight. 

In many cases, the weight that you see on the scale doesn’t represent your fat mass, but a reflection of how much water is being held by your body. 

The low thyroid state is one that encourages the retention of water

Sometimes that water is retained in your face, sometimes in your legs, and sometimes in your belly. 

Many thyroid patients are astonished to find that they may be holding an extra 5-10 pounds of water weight that gets flushed out once they optimize their thyroid. 

When you combine this water weight with the fat that comes from the other things I just mentioned, it’s easy to see how your thyroid alone can make you 20-30 pounds heavier. 

Getting rid of this fat is all about using the right treatments.

And if you want to see which are the safest and most effective for thyroid patients, then check out this article next

Scientific References

#1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911848/

#2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8259075/

#3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3205882/

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC377492/

#5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5421125/

why thyroid patients get fat & how to stop it

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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 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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