How does the body decide where to add or take away fat when gaining/losing weight?



How does the body decide where to add or take away fat when gaining/losing weight?

In: Biology

It doesn’t ‘decide’ per-se. Fat is distributed in a rough order that varies with your sex. Males for example are more likely to store fat in their upper-body and abdomen (hence the Beer Belly phenomenon) whereas Females are more prone to store it around their hips and thighs. This is what largely contributes to the ‘pear’ shape we associate with women.

Males are also more likely to store ‘visceral’ (around the organs) fat which is what results in the skinny-fat phenomenon where people can be overweight, but not look it. Females are more likely to store fat subcutaneously (under the skin) where it’s more noticeable. This combined with our bodies preference for storing fat in certain places is what contributes to the difference of appearance as a result of our weight.

Places like your face, neck and arms are lower down the list. Which is why when someone gains/loses a lot of weight this is where you notice it. It’s one of the last places for fat to get stored, but when you start losing weight that means it’s one of the first places to go.

When you lose weight, it comes off in the reverse order that it went on. So if you’ve noticed that you’ve recently started accumulating mass in a certain place, then with improved diet and exercise that is the exact place it’ll start coming off first.

Edit: The order I’ve given is more of a broad trend rather than something you can usefully apply to individuals, various generic and environmental factors will affect the order from person-to-person. Your personal order may be different, but regardless of the order it’s a last-on/first-off system.

Edit2: There’s some back and forth in medical journals about whether there is *any* consistency to the order or if it’s purely an individual/genetic thing. I’m not qualified to really judge that and deep dive into them so please take that particular claim with a few pinches of salt. But while the notion of a consistent order seems contentious, there is nevertheless an order for you.

TL;DR – Fat goes on in a particular order on different parts of your body that varies between people, and it comes off in the reverse order that it went on. Areas like our belly/hips are often the first place it goes on (but not for everyone!), so it’s the last place it comes off and you have to do everything else first.

It is mostly genetic and changes with body types. You can’t burn fat from spesific places either. You can’t burn only tummy fat for example. You can however add some muscle mass for a neater look.

You have a set number of fat cells in your body. Depending on your genetics there may be more or less of them in certain parts of your body. If you gain more body fat, you’re not gaining cells, they’re just getting bigger. The same with losing body fat, those cells get smaller. They more or less all grow and shrink at the same rate.

Something that is not already discussed, the body temperature raises and burns both fat AND muscle. Different types of diets and exercise also burn calories differently.

For instance, High Intensity Interval Training works the heart extremely well, and more fat is burned than muscle. Extreme long distance cardio, by the end, can burn near equal amounts of muscle and fat. Any exercise (and I do mean any, as long as it’s not a smartass response) is good for visceral fat control, which is the biggest indicator for long term health issues, when it comes to fat that is. The problem is, it requires tests (blood draws) to determine where an individual is.

Diets, well those are very tricky. The field of study is fraught with profit engineering, name recognition, and questionable statistical conclusions. Almost every study is countered with another, and all have the potential of being correct or incorrect. In the end, regularly see your doctor about your health.

Edit: correction from subcutaneous to visceral. I mixed them up.


Your hormones, estrogen and testosterone levels will dictate where your body decides to store and therefore burn fat first. Which is why food quality is important not just macro nutrients. Poor quality foods and lack of sleep tend to have a negative effect on hormone balance. Among other environmental factors.

While most of the responses itt are accurate as far as our current medical understanding is concerned, [biochemists are making a lot of progress in understanding the signaling pathways that regulate lipolysis,]( and several proteins have been identified that are associated with fat burning. [There was an investigational peptide that appeared in a paper a few years ago]( but very little follow-up was done and the project was abandoned. You can find fraudulent knockoffs of the drug on sketchy dieting aid sites.

Which places depends on physiology and genetics. You don’t have much control over that. How much depends on exercise. Basically proportional to muscle mass and endurance capacity. For synergistic results, you need to do both: strength training + cardio.

Marathoners will have very low body fat because they’ve trained their bodies to use fat efficiently as a source of nutrition during exercise. Vigorous exercise can also stimulate body to deposit excess energy in muscle glycogen as opposed to fat. This is why if you’re in great shape, it’s easier to stay in shape; you’ve already altered your metabolic profile to something kind of favorable. You can usually reshape your metabolism, if it is out of whack, but this requires *work*. A mile run a few times a week or arm curls aren’t going to cut it. Unless you’re basically 20.

You don’t have to run marathons or kill yourself at the gym to have low body fat (reshape your metabolism). Combining strength and cardio training about 1 hour every other day will lead to substantial fat burning. Make sure to target all large muscle groups for the most benefits. If you want the benefits but don’t want to spend much time, you can do high-intensity interval training instead. Those workouts tend to be 30 minutes or less. However, they are much more challenging and more people would probably prefer the longer workouts, I think.

EDIT: Since most people in this thread don’t seem to know much about exercise, and since it is getting to be that time of year again, I just want to throw out there — if you’re out of shape and looking to start getting in shape — especially with the warmer weather — I highly recommend you DO NOT start by running. Running has probably one of the highest injury rates in sports — about 33 to 75% of people are injured annually. If you’re large (fat or tall) your risk is higher. If you have history of running or you are small in size — by all means go ahead. It’s just I see a lot of people try to get started by throwing on old jogging shoes and sweat pants and plodding through the neighborhood. God bless em for trying. But honestly, even though it’s popular I think it’s a pretty poor place to start if you’re not already kind of light and used to the impact.

It’s like letting air out of a balloon. But, not every balloon has the same shape. Some parts deflate faster than others and it depends on the particular balloons shape.


It’s a complicated question with a complicated answer that varies as much as your genes do. The simple answer is hormones! Hormones are chemicals in your body that tell your body what to do. There are lots and lots of hormones that all have different functions that interact with each other, you can learn more at

That said, while hormones tell your body what to do, they don’t really decide where anything goes. Your genes sorta do? Your genes kinda write the code that your hormones function on, and sometimes that code gets a little twisted up. There can be mutations and disorders that make your hormones behave in odd ways, some of which might be really subtle, so subtle that no one notices unless they get their genes sequenced.

Generally speaking, you can’t pick and choose where your body stores fat, you can’t work out your mid section to burn belly fat, for example. You can’t get a six pack from doing a lot of abdomenal exercises. Without surgery you can’t have a six pack while also maintaining the fat in your ass. It’s a lot like ocean water levels, like it rises together everywhere, not just in specific places. It just seems like you flood in certain places only because some places are lower-lying than others. Some areas of your body are meant to have more fat in it than other places, and this can also be genetic thing

Cis women and in general people with higher estrogen levels have a higher body fat percentage that is about double the norm for cis men. Subcutaneous body fat plays an important roll in hormone regulation, especially estrogen.

There are a number of conditions that affect how your body places and metabolizes excess fat, often these involve hormones and have a genetic component. Lipedema is a condition that a lot of people don’t know about but it’s actually pretty common, it mainly affects women. Fat stores in the lower half of your body and you literally can’t lose it, and it can be quite painful and get worse with time.

The ELI5 answer is – it doesn’t. It’s like trying to empty a lake with a bucket. You don’t leave a bucket shaped hole in the water; the surrounding water is redistributed to fill in the space made by removing the water.