Body Fat Hormone Guide: What Your Body Fat Is Telling You

Body Fat Hormone Guide – What Your Body Fat Tells You About Your Hormones

Where You Gain Fat Tells you A Lot About Your Hormones

YouTube video

Most people are concerned with being overweight but they pay little attention to WHERE the fat on their body is accumulating. 

This is a huge mistake. 


Because the location of the fat on your body can give you valuable information about what type of hormone imbalances that you have. 

It works like this:

Certain hormones direct and dictate where your body is going to store fat. 

Under normal circumstances, you may expect to have a generalized distribution of body fat all over your body as you gain weight. 

But that’s not what happens to most people. 

Instead, they notice that the fat that they gain is unevenly distributed and often is in one area more than another. 

Think of a woman who is gaining weight more in her butt and thighs as opposed to her abdomen (1). 

Other women may gain weight primarily in their chest and so on. 

This same concept applies to men as well but today we will be focusing more on women because they tend to be more affected. 

Why does this information matter?

Because it gives you valuable information on your hormone levels. 

Certain hormone imbalances tend to result in weight and fat gain in certain tissues. 

So you can look at your body and reverse engineer what type of hormone imbalances that you are struggling with. 

This is a very valuable tool to you because it can help direct the type of treatments that you undergo and/or the type of hormones that you may want to consider taking. 

Many doctors, especially the so-called “hormone” experts such as endocrinologists, don’t take hormone imbalances seriously and may not even be able to help interpret your hormone levels. 

Using this body fat hormone guide you can get a much better idea of what type of hormone imbalances you are struggling with which can ultimately help you lose weight and normalize your body. 

You will find this information particularly helpful if you are someone who is trying to lose weight with calorie restriction but still find that you have some stubborn areas that don’t seem to get better. 

Body Fat Hormone Guide:

A couple of things before we jump in…

#1. You need to realize that this is a generalized guide.

This information tends to be fairly accurate but it’s not a complete substitute for getting your labs checked. 

In addition, you should be aware that there can be a lot of overlap between hormone problems. 

For instance, both cortisol and insulin can lead to belly fat and abdominal fat. 

In order to completely get rid of your belly fat, you may need to address BOTH conditions. 

#2. Most weight gain is driven by your hormones and NOT the calories that you consume.

Many people assume that the predominant cause of weight gain is related to calorie consumption. 

Calories are important but more important is the source of those calories and how the food that you put into your mouth impacts your hormone levels. 

For instance:

Eating highly processed foods high in sugar is likely to result in insulin resistance which will lead to weight gain and that weight gain will likely be directed to the abdomen (2) because that’s where people with insulin resistance tend to store their fat. 

It’s not the calories so much as it is the TYPE of calories that you are consuming. 

Having said that, calories are still important and they shouldn’t be completely ignored. 

#3. It’s still helpful to get your hormone levels TESTED.

This guide works best when it is combined with your serum hormone levels (or hormones tested via another route). 

For purposes of this article and your body fat, here are the hormones that you will want to get your doctor to order for you:

They aren’t required, but they will be very helpful if you have them to look at as you go through this guide! 

#4. Genetics still play a role and are still important.

At the end of the day, there may be aspects of your genetics that dictate where your body stores fat. 

Or, more likely, your fat storage will be a product of a combination of both your genetics and hormone imbalances. 

There may be some areas of stubborn fat that simply don’t respond to hormone management because they are due to your genetics (3). 

With all of this in mind, let’s jump in:

Fat on the Upper Arms and/or Lower Legs

Do you find that your body fat tends to accumulate in your upper arms and or lower legs?

I’m talking about the bicep/tricep area of your arms and the calf area of your lower legs. 

Fat in the lower legs (calves) and the upper arms (triceps/biceps) tends to be heavily influenced by your sex hormones, namely progesterone, estradiol/estrogen, and testosterone. 

Fat in this area tends to be very stubborn and difficult to treat. 

To make matters worse it can’t be targeted, either. 

For most people who have fat in these areas, fat loss here tends to occur last. 

For instance:

If you are someone who is 50 pounds overweight and you lose that weight, the extra fat that you have in your calves and upper arms will probably be the last area that you see weight loss occur. 

You will see fat loss occur in your chest, abdomen, back, and upper legs before you see fat loss in this area. 

I have had success in treating fat in this area using a hormone called hCG which stands for human chorionic gonadotropin. 

hCG is a hormone that can be used to help regulate sex hormones including estrogen and progesterone imbalances and may help somewhat “target” fat in this area. 

Using hCG is completely different from the hCG diet, by the way. I’m talking about using this hormone by itself as a weight loss therapy, usually combined with a whole foods diet and other treatments/medications/hormones. 

Fat in this area probably has a strong genetic component which is why many people resort to liposuction to eliminate the fat after attempting healthy diet and exercise. 

This may be an option for that stubborn genetic fat but it shouldn’t be used unless you have FIRST tried to balance your sex hormones. 

Abdominal or Belly fat

Fat in the abdomen and or/belly area is fairly straightforward and common. 

Fat in this area is almost always related to either one or both of these hormone imbalances:

Insulin resistance or cortisol dysfunction (or an adrenal problem). 

Concentrated belly fat is actually a good thing because it’s fairly easy to treat this problem, especially when compared to some other areas that we will be talking about here. 

If you are someone who is 20-25 pounds overweight and 80-90% of that fat is targeted in the belly area then there is a big chance that you have one or both of the hormone problems I mentioned above. 

Insulin resistance and cortisol problems tend to come in a pair. 

Insulin resistance comes from eating foods that are naturally high in refined and processed sugars including things like bread, pasta, pastries, sugary sweets, and so on. 

Because the average American consumes way too much of these types of foods, insulin resistance is found in up to 50% of the population (4). 

So if you are reading this then there’s a good chance you have at least a minor issue with insulin resistance. 

Cortisol issues, on the other hand, tend to come from stress. 

If you are like most people then you are probably under a low amount of constant stress. 

A little bit of stress is good and can rev up your body. But too much stress can lead to cortisol issues which can exacerbate insulin resistance and lead to weight gain in the belly all by itself. 

But often these two hormone imbalances are seen together because stress leads to insulin resistance and things that are stressful tend to cause poor eating habits. 

Things like not sleeping enough or relying on coffee as energy can reduce willpower and lead to snacking on unhealthy foods which are high in sugar. 

The good news is that treating cortisol and insulin resistance is typically not that difficult. 

You can manage stress by taking things like adrenal adaptogens and adrenal glandulars, in addition to ensuring you get enough sleep each night and you take time for yourself. 

Insulin resistance, on the other hand, can be treated with diet (low carb, ketogenic, carnivore, etc.), supplements (such as berberine, alpha lipoic acid, glucomannan, fish oil, etc.), medications (such as Victoza, metformin, Saxenda, and acarbose). 

There really aren’t very good prescription medications that will treat a high cortisol level but you can use supplements such as phosphatidylserine to help in that area. 

Fat in the Trunk and Neck Area

Fat in the trunk and neck area is almost exclusively caused by problems with cortisol. 

If you aren’t familiar with the terminology of truncal obesity (5), it refers to fat that is localized in your chest, abdomen/belly, and back area, pretty much anywhere on your trunk that isn’t your arms and legs. 

And by the neck, I am really referring to weight gain in the back of the neck area. This is sometimes referred to as a buffalo hump if it gets big enough. 

Fat in either of these areas is usually caused by cortisol issues. 

But in this case, the cortisol issue causing this type of obesity is a bigger issue compared to the cortisol that causes abdominal fat. 

The type of cortisol issue that causes abdominal fat is minor and may not even cause problems in your serum cortisol level. 

This type of cortisol problem is usually referred to as adrenal fatigue because there are issues in how cortisol is being used by the body but that problem is typically not manifested as big changes in your serum lab level. 

Those people who have truncal obesity and fat in the neck area typically have a sufficiently big enough problem with cortisol that their serum cortisol level is marked or flagged as high when it is tested. 

This sort of fat accumulation may be a precursor to medical conditions such as Cushing Disease (6) and may indicate that you have a bigger or more serious problem that needs to be evaluated. 

Because of this, fat in this area is not quite as common as some of the other areas we will be discussing. 

Decreased Muscle Mass or Inability to Build Muscle Mass

I know we’ve spent time talking about body fat but it’s almost important to consider your muscle mass. 

Body fat and muscle mass really go hand in hand with one another because both of these tissues compete with each other for your calories. 

Think of it like this:

If your fat is winning then your calories will be going into your fat cells which makes them bigger. At the same time, they may be taking calories away from your muscles which may cause them to shrink slightly. 

If your muscles are winning then your calories will be burned up by your muscle tissues as a source of energy and more fat will be burned up instead of stored so your fat cells will shrink in this process. 

As someone listening to this, you pretty much always want your muscles to win in this war for calories because it means you will be losing weight!

For this reason, we actually care about your muscle mass. 

There are a lot of women who struggle with the ability to BUILD muscle mass even while regularly going to the gym, lifting weights, or exercising. 

These women often suffer from decreased muscle mass or the inability to build muscle mass and this very problem is usually an indication that you have an issue with testosterone. 

Low testosterone levels, in both men and women, cause this very issue. 

Testosterone helps your body build lean muscle mass (7), helps support your mood (8), supports your sex drive (9), and helps manage your metabolism. 

Many women suffer from low testosterone so this hormone should never be neglected!

If you recall, I mentioned in the beginning that low testosterone may lead to fat on the upper arms and or lower legs. 

Fat accumulation in that area tends to be due to a combination of problems in all 3 of the hormones listed there, namely estrogen, progesterone, and testosterone. 

Issues with building muscle mass tend to be an isolated hormone imbalance where your estrogen and progesterone may be fine but your testosterone is lower than it should be. 

So keep that in mind as you evaluate your hormones. 

You can treat low testosterone with the use of bio-identical testosterone replacement. 

And yes, women can safely use testosterone as well!

TRT (testosterone replacement therapy) in women is fairly easy but the doses used in women are typically much smaller than those doses used in men. 

TRT works quickly to elevate your testosterone level so many people see results in 1-2 months. 

Whole Body Fat (generalized fat evenly distributed across your entire body)

By whole body fat what I mean is that you have a relatively even distribution among all areas of your body when you gain weight. 

This means your fat is distributed somewhat evenly in your chest, abdomen, butt, back, legs, arms, etc.

With this sort of weight gain you really just see an outward expansion of your entire body as you gain weight everywhere. 

This type of fat gain is fairly common and tends to be caused by 2 major players:

#1. Thyroid problems

And #2. Leptin resistance or leptin issues. 

Because your thyroid controls and regulates your metabolism (well, about 60% of it) if you have thyroid problems then you will see a generalized decrease in your metabolism. 

This reduction in metabolism will typically lead to weight gain all over. 

Thyroid problems typically do NOT cause weight gain in specific areas for this reason. 

The other hormone listed here, leptin, is very important as it relates to weight gain. 

In my experience, leptin is probably one of the most important hormones for managing your weight and may be a driver of weight gain in most people. 

Think of it this way:

If you are overweight and unable to lose weight then you have a leptin problem. 

Leptin resistance, the flavor of hormone imbalance that this hormone comes in, reduces your body’s ability to burn fat and tends to cause generalized weight gain over your entire body, much like thyroid problems. 

What can be confusing, though, is that it’s fairly uncommon for someone to JUST have leptin problems. 

In other words, if you are overweight for any reason or from any hormone imbalance, this weight gain will be associated with leptin resistance plus whatever hormone imbalance you are struggling with. 

To make things even more confusing, thyroid problems can lead to estrogen/progesterone/insulin issues and it can even make leptin resistance worse. 

Here’s a fairly typical scenario:

Imagine that you start out with a thyroid problem (low thyroid) that leads to a generalized weight gain of 10 to 15 pounds. 

This weight gain will be fairly generalized over your entire body and evenly distributed. 

But, after about 6-12 months, your thyroid then causes estrogen and progesterone imbalances that lead to weight gain in your upper arms and lower legs. 

Even though you first started with a thyroid problem, your hormone problem evolved over time and which led to changes in your body fat distribution. 

This sort of thing is very common, by the way. 

For these reasons, if you find that your situation is confusing, it would probably be a good idea to get ALL of your hormones tested so you can tease out the major players contributing to your weight gain. 

Fat in the Thighs/Butt/Gluteal/Breast Region

If you are struggling with weight and fat gain in the thighs, butt, and breast region then your problem is almost always caused by an increase in estrogen. 

Estrogen is probably one of the most important hormones found in women. 

It is responsible for softening a woman’s skin (10), for providing subcutaneous fat in the face which gives the face a round attractive appearance, it’s responsible for the development of the butt and breast area, and much more. 

But these things only happen if estrogen is balanced. 

Things can go wrong in a hurry when you have too much estrogen. 

Because estrogen stimulates fat tissue and can cause certain fat cells to grow, too much estrogen causes certain estrogen sensitive tissues to grow more rapidly than others that don’t have as many estrogen receptors. 

In women, excess estrogen usually results in the growth of the breasts (think of what happens during your menstrual cycle or during pregnancy), in the butt region, and in the thighs. 

Excess estrogen, known as estrogen dominance, can lead to rapid growth of these areas and result in body fat physiques such as the pear shape. 

Estrogen dominance refers to a syndrome in which your body is being overstimulated by too much estrogen.

And this syndrome is quite common. 

Foods, hormones, medications, and chemicals all can have an estrogenic effect and may tip the balance in favor of too much estrogen in your body. 

Compounds that do this are referred to as estrogenic or xenoestrogens (11) and they should be avoided if you are a woman. 

You can also get excess estrogen in a roundabout way, through low levels of progesterone. 

Estrogen and progesterone are meant to balance one another so if you are too little progesterone, with even normal amounts of estrogen, this creates a relative estrogen dominance syndrome which can lead to the body fat accumulation noted above. 

Managing estrogen dominance is possible and can be done by finding the source of excess estrogen in your body. 

For some that may mean losing weight and eliminating foods that have estrogenic activity. 

For others that may mean using bio-identical progesterone to balance their estrogen levels. 

Rapid Weight fluctuations Up and Down over a Short Period of Time 

Lastly, we need to talk about weight fluctuations. 

Weight fluctuations are important because they impact your weight but they typically do NOT impact your fat mass! 

Pretty much everything we’ve discussed today impacts your weight but I haven’t really focused on fat mass specifically. 

Most hormones DO impact your fat mass which impacts your weight. 

But there are some people who experience weight fluctuations that are unrelated to their fat mass and are instead related to something else, usually water weight from hormone imbalances. 

As an example, there are many people who will reach out to me and tell me that their weight goes up and down by 5 pounds or more within a few days or even in one single day. 

This type of rapid weight gain is almost ALWAYS related to fluid shifts in the body. 

Fluid shifts because your body is holding on to more water and that water is staying as bloating or because you are holding onto more water because of something like constipation. 

It’s almost impossible for a shift in 5 pounds in a single day to be related to an increase in fat mass. 

What can cause this sort of rapid shift? 

A few different things can but when it comes to hormones there is one that is often responsible for such rapid weight gain and that’s progesterone. 

One of the effects of progesterone is to act as a diuretic which helps your body eliminate extra fluid. 

Changes in your progesterone level can, therefore, impact fluid levels in your body. 

Progesterone is one reason why you can fluctuate several pounds during your menstrual cycle! 

It’s not an actual gain of fat mass but instead retention of fluid and water. 

How to Get Target Fat On your Body

For the most part, it isn’t really possible to target areas of fat on your body. 

The idea of going more crunches to “burn” belly fat is definitely not going to work. 

Having said that, it may be possible to indirectly target these areas by focusing on your hormones. 

Typically, when done correctly, balancing your hormones leads to fat loss in the entire body with a more targeted effect on certain areas depending on whatever hormone imbalance you are targeting. 

Always remember that your hormones are incredibly powerful and they serve an important purpose in your body. 

These hormones help to regulate your metabolism, your muscle mass, where your body stores fat, how your body processes sugar and nutrients, they send signals to your brain to automatically adjust caloric burn, and much more. 

This all assumes that your hormones are working as intended!

When you put extra stress on your body, when you consume foods that are processed and heavily manipulated for flavor and calories, when you fail to do essentials things such as ensure you are getting enough sleep, you will see a breakdown in how your hormones are intended to work. 

When this happens, you will start to see extra weight gain in the areas that we’ve discussed here. 

The best way to address these issues is with a knowledgeable doctor that can help guide you back to a balanced and normal state. 

Using bio-identical hormones such as progesterone, testosterone, and thyroid hormone can help. 

Some people may also find a benefit in adding prescription medications as well. 

No matter what, though, you need to make sure you are taking care to control inputs such as sleep, stress, healthy eating, and exercise. 

Now I want to hear from you:

Are you struggling with an abnormal pattern of weight gain?

What do you think your weight gain is telling you about your body or your hormones?

Have you had your hormones tested? 

Are you taking any bio-identical hormones already?

Share your questions or comments below! 












what your body fat means for your hormones

Dr westin childs photo

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.

P.S. Need more help? Check out my free thyroid downloads and resources.

17 thoughts on “Body Fat Hormone Guide – What Your Body Fat Tells You About Your Hormones”

  1. Dr Childs,

    Well, as everyone says, my case is interesting…. 🙂

    I’m 53, so menopausal and gained weight in belly fat, thighs, breasts, upper arms and calfs . So I guess, overall. Well, previously gained belly fat. I had tummy tuck & breast lift, July 2020 .. not gaining in belly, but breasts increased a little after mastoplexy.

    Labs show menopause and estrogen dominance – started BHRT 2 months ago. Thyroid panel not in your optimal range. Vit D very low, cortisol high (even though I think I handle stress well), leptin and insulin just slightly elevated based on your optimal levels. Started high dose vit D and other multi vitamin. Also, morning temp = 96.8-97.2.

    So, new MD thinks there’s HPA dysfunction and is also suspicious of CIRS – I don’t think any chance of CIRS.

    I have started weight sessions, but not sure I am building muscle which I used to do pretty easily. I walk 3 miles daily + slow 12 min jog for 1 mile.

    I think I have multiple hormones out of whack. I will be pushing doctor to treat thyroid, preferably not levothyroxine. Expect increase in BHRT (est,protest, Test) at next gyn appt. would like ldn to treat weight set point along with addressing leptin, insulin and cortisol. Whew!

    Any other ideas I should pursue with hcp? since I won’t typically gain in the belly, I can’t completely go by your guide above? I need to lose 25-30 lbs.


  2. Hi I was told on 2013 I was hypo they put me on levo 25 mcg was on that for years. had a lot of stomach problems 2012 h-pylori got rid of that still had stomach issues on and off my whole adult life. but in 2015 it got worse my dr was telling me at this point it was because of my last kid shes 25 my issue was constipation belly pain and if i laid down on my back when i raised up it went to a elongated point and it was hard and it just kept getting bigger so in june of 2016 I went to a specialist he took ct scan and found the mass in my stomach so he sent me to pheonix to the mayo clinic long story short it was 10,000 liters of fluid but it was my ovary so he did a oophorectomy. After that i was good until september i got sick fever i mean i was sick went to the dr they did blood work they gave me steroid shots antbiotics nothing helped still running a fever still couldnt breath more blood work nothing worked went chest x ray they said i had a blood clot to go to the er so i did they couldnt find nothing still running a fever i could barley walk i hurt all over it was awful they took more blood still nothing this is oct 31st so i was just done ready to just go home and die. Then my freind told me about this wellness place out of town so i called wich they had to have blood work and i had to wait 6 weeks to get in but it was worth it I had EBV and diagnosed me with hashimoto thyroiditis so when she looked at my blood work I didnt have any of my hormones that you need it took just that little time to run out so she put me on bio hormone pellets and nature throid and oh my i was great but now they have removed nature throid so I take armour and it just isnt giving me my energy i crave sweets like crazy
    I dont have the same dr its still the wellness some just dont quite understand the hashimoto . I DID ORDER THE HASHIMOTOS BUNDLE AND DID A SECOND ORDER FOR THE BERBINE
    do you see patience
    where are you located at
    i am just so scared of getting like i was before
    Thank you for doing all you do.

    • Hi Jeanette,

      I do not see patients anymore and it sounds like you are on the right track! I would make sure to try and find a doctor just to keep tabs on your hormones and thyroid, though, and in case you need any prescription medications.

  3. hi – new to your site and it is like you’re speaking to me personally…I’ve been on the phentermine train and lost 40 lbs. 6-7 years ago – felt amazing! then took a new (stressful) job and slowly gained it back. The pandemic took me over the top and right back where i started. I was almost ready to go back on the phentermine until i watched your YouTube on it. I was diagnosed with Hashi during the pandemic by an endocrinologist and my family dr. put me on Levo 25 mg begrudgingly telling me she didn’t really agree with his diagnosis. I do not feel like it helped and my hair loss is getting worse. I stopped taking it a few days ago. the problem is I dont know where to start. no matter what I do the weight does not come off and I am definitely one who can gain 5 lbs in a matter of 2-3 days. I’m typicallly paleo/carnivore but lately it isn’t making a different what I do. can you tell me which program to start with?

    • Hi Cheryl,

      I would recommend starting by checking your thyroid + other hormones. From there you can determine which diet would be best and if additional therapies/medications are necessary.

      If you think you have significant metabolic damage then I would also check out this post:

  4. Hi Dr. Childs, I’d like to first of all, thank you for the amazing job you are doing in helping so many of us. Your wisdom is certainly God given, and I feel so blessed to have this information available. I am struggling with my weight like never before and I am completely confused on where to start, and what to do because, so far, nothing has worked. I am 61 yrs old, I was diagnosed with Hashimoto’s in October 2009. At that time, I was very active, spinning and the gym for 2 hours, 4 times a week, I was very slim and fit. By the end of 2012, I had started gaining weight and the only thing I was doing different is that I was no longer going to the gym, but my diet was the same as before, when I had no weight problems. To make a very long story somewhat short, I have gained about 50 lbs. and my frustration is that I continue eating the same as when I was fit and slim. I have a bio-identical testosterone pellet implanted every 4 to 6 months, and use bio-identical progesterone cream every night. I had labs done not too long ago and I am no longer insulin resistant, my A1C is normal, my cortisol is no longer low (was very low for years) but in perfect range. But my leptin is super high, and after reading this article, I am convinced this is my problem, can you advise me on which program to start with? I very much appreciate your time and help.

    PS. I take 112 mcg Tirosint, 10 mcg Sustained Release T3 and 4.5 mg. LDN since 2017.


  6. Dr. Childs,

    After I had my first child at 32 I started gaining a lot of weight around my trunk and on the back of my neck (buffalo hump as you said). Fast forward to finishing a 1/2 Ironman at my fittest and at 125 lbs & 5’6″, I still had 30% body fat. I do have Hashimoto’s, and my morning cortisol was 0, even after I had a very stressful evening, and actually ran to my blood draw appointment at 8 am. No one knows what to do with me or why I have such high body fat as a fit and healthy person with no comorbidities.

  7. I know this is a late comment so I’m hoping you’ll see it. My 15 year old daughter has a significant amount of belly fat despite eating a unprocessed WAPF-type diet (gluten and dairy free except butter.) She has hashimoto’s antibodies but her TSH is 4.5 so they won’t give her medicine. According to the doctor, she also has pcos but there are no other symptoms of it. She wants to lose weight but she already eats extremely healthy. We’ve just started going to the gym to lift weights and she takes Ovasitol, Magnesium, cod liver oil, and low-dose Naltrexone. Is it healthy for a teenage girl to eat low carb (physically or mentally–she already feels like a weirdo)? It doesn’t make sense for her to be so heavy when we eat so healthy (and she doesn’t overeat at all.)

  8. This was an excellent article on where body fat is located gives us a clue as to what is going on? What about extra fat around the knees (primarily above and on the sides)? No amount of exercise or walking seems to even make a dent in it. I’ve had that since a teen but now in my 60’s its much worse and the imbalance visible. (I do have bone on bone in one knee, but not both, and this fat knee phenomena preceded the wear and tear of cartilage by decades.) Suggestions? Thank you

  9. Dr . Childs, you defined each type of fatty area and possible treatments. You touched on truncal fat, said it was probably cortisol related, and then kept going. I have been gaining weight in my trunk, back and am getting a fat pad on the back of my neck. I am taking levothyroxine, managed by my dr. He pretty much ignores what I ask and tell him and says my levels are “good”. What can I do, for my own health?


Leave a Comment

Your Cart
Your cart is emptyReturn to Shop
Calculate Shipping