How Your Genes Affect Your Jean Size

By , Molly Galbraith
"I am just big-boned. Everyone in my family is big-boned."

"My Mom is heavy. My Dad is heavy. I'll never be anything but heavy."

"My sister has my Mom's lean body and I have my Dad's stocky body, so I will never be lean like her."
At one point or another, you've probably heard your friends or family members utter these phrases. Heck, you may have even said similar things yourself. 

So just how much of a role do genetics play in your body shape and size? If you have heavy parents, are you truly doomed to be heavy forever? When your parents are tall and lean, can you get away with eating more—without consequence? If your mom has wide hips, will shopping for jeans always be the bane of your existence?

First and foremost, yes, genes do play a significant role in your body type, shape and size. There are three generally accepted body types: ectomorph, mesomorph and endomorph. Below is a table listing general characteristics of each body type.

3 Main Body Types
Features Ectomorph Mesomorph Endomorph
Appearance Slender & lean Muscular & athletic Soft or chubby
Shoulders Lean & narrow Wide Narrow to medium
Body fat Low Varies Average to high
Bones Small Large Medium
Metabolism Very fast Medium to fast Slow
Waistline Straight Hourglass Large
Gender Men & women Mostly men Mostly women
Weight gain Difficult gainers Yes, if overeating Easily gain weight
In general, if you are thin, have long limbs and a long neck and low body fat levels, you are an ectomorph.

If you would describe yourself as an "athletic" build, and it's not hard for you to add body fat or muscle mass to your frame, you are a mesomorph. The mesomorphic body type is more common among men than women.

If you have a softer, less athletic build, with larger hips and thighs, and you tend to easily gain weight, you are an endomorph. The endomorphic body type is more common in women than men.
In addition to these three main body types, there are other general body shapes that describe how people carry or store body fat. You've probably heard people referring to themselves as "apple" shaped (tendency to gain weight in the midsection but have lean limbs), "pear" shaped (tendency to carry weight in the lower body) or a general "avocado" shape (a mix between an apple and a pear). 

While reading through the descriptions above, it's only natural to try and figure out which category you fit into. You might have found one that sounds exactly like you and your build. Or maybe it wasn't so clear which one you were. Very few people are one "pure" body type. Usually, we have some characteristics of one or more categories. I am a meso-ecto hybrid. I am very tall with an athletic build, broad shoulders and a narrow waistline, much like a mesomorph.  At the same time, I have very long limbs, long and thin fingers and a long neck; all ectomorphic characteristics.

Hybrid body types are quite common and if you found yourself nodding along to characteristics in two of the different categories, you are likely a hybrid.
So why does it matter?

Because so many of us bemoan our body shapes and try desperately to change them. But here's the truth about re-shaping your body. We are all born with a specific genetic makeup, a unique "code," (based on our parents, and our parent's parents, and their parent's parents) that we cannot control. We cannot change our body from an apple shape to a pear shape. We cannot control whether we gain muscle easily or if it takes every ounce of our effort to put on just a little bulk. We cannot control if our frame is small or our hips are wide. No matter what we do, our bodies will be built and shaped a certain way.

What we do have some control over, however, is how those genes express themselves.

Think of your genetic code as thousands of light switches on a wall. The individual light switches you have represent predispositions to certain physical characteristics from your height to your bone structure to your body fat levels. So what determines which lights flip on and which stay off? Your environment and lifestyle. Here are a few examples:
  • A young girl who comes from a tall family may be pre-disposed to being very tall, but if she experiences malnourishment during childhood, her growth can be stunted and she may grow up to be short or average height.
  • A man whose parents are both very lean (even without trying) may find himself carrying a significant amount of excess body fat if he spends many years making poor food choices, eating in excess and living a sedentary lifestyle.
  • A woman who is pear-shaped and tends to gain body fat in her hips, butt and thighs may never have "small" hips or a flat butt—no matter how hard she tries. But she can stick with a healthy diet and fitness program to reduce the amount of body fat that is stored in her lower body.
  • A man who comes from a long line of obese family members isn't necessarily destined to be obese himself, although he may have a "light switch" for easy fat storage. With diligence and hard work at watching his food intake and burning extra calories through exercise, he can keep weight gain at bay. But it may take him more work than someone else with different genes.
Then you have me and my naturally curvy figure. As I mentioned above, I have broad shoulders and a small waist. I also have large breasts, wide hips and a tendency to carry excess body fat. I'm more pear-shaped than apple shaped, so while my belly can be lean enough to show abdominal definition, my thighs still tend to be "thicker" even when my body fat levels are normal or low. Several members of my family have struggled (or currently struggle) with their weight, and I used to struggle with my weight as well. However, now that I know how to eat and exercise properly, I am able to control my level of leanness to some degree. This means that while I may struggle to get extremely lean, I am able to alter my lifestyle to avoid being overweight or obese.   

Truly, I have run the gamut from my highest to lowest weights, but my body is happiest somewhere in the middle; maintaining a healthy weight without going to extremes.

Genetics are a big determining factor in many of our physical characteristics, but that doesn't mean that we should give up and resign ourselves to a certain look because of our parents. However, it's important to know that you can't switch from one body type or shape to another. When you set body goals that go against your natural tendencies or "light switches," it can take extreme levels of work and diligence to get there or maintain that state. And when you make a choice to go against your natural tendencies, it can be a stressor to your body. Your body may never be comfortable there. Your body will take any chance it gets to revert to what feels more comfortable and natural.
For a pure ectomorph, gaining mass of any kind (fat or muscle) can be a full-time job requiring upwards of 4,000-5,000 calories a day, for years at a time. Someone with this body type would struggle to be a successful bodybuilder or linebacker.

On the other hand, a person with a mesomorphic body type has little chance of ever being slim and petite. If you're born with this body type, being a ballet dancer or jockey is probably not in the cards for you.

If you are born an endomorph, it will be much more difficult for you to get as lean as your ectomorph and mesomorph counterparts. You are unlikely to have a career as a bikini or runway model.

If you have more of an apple-shape, it will be difficult, if not nearly impossible, for you to attain visible "defined" abs.  As you lose body fat, your limbs will lean out first, and the fat on your stomach will be the very last to go, thanks to the shape you were born with.

These statements may feel like cold, hard truths, but they are not meant to demotivate you. These generalized statements are more for your own sanity: things to think about when you set your own weight-loss or body-shape goals. They are a glimpse of the reality you may face if your body goals are "extreme" for the genetic cards you were dealt. Yes, it's possible to totally transform your body in a lot of ways. But is it really worth it? Only you can decide.

I've learned from experience, that I don't want to go to those extremes. For me and my curvy figure, competing in figure competitions and trying to get extremely lean was a huge stressor on my body. In fact, the three times that I tried to achieve an extreme level of leanness when I prepped for different figure competitions, my body fought back. Hard. 
I may have looked extremely lean, but I felt awful.

I found myself exhausted, depleted, and without a period for months at a time. And once I resumed more normal eating and exercising patterns, my body weight and body fat levels exploded. I barely recognized my own body. After my third competition, I had caused my body so much stress that it broke down and I was diagnosed with Hashimoto's thyroiditis, PCOS (polycystic ovarian syndrome) and adrenal dysfunction.

Since my diagnosis, I have learned to love and accept my curvy body, and I no longer try to force it to attain uncomfortable levels of leanness. I simply maintain a comfortable, but not extreme, level of leanness through proper eating and consistent, intelligent exercise. 
I've finally found a happy middle ground for my body. My weight fluctuates a bit depending on the season and my training, but this is where my health, performance, aesthetics and lifestyle intersect. 

The bottom line is that both genetics and your environment are key factors in your health and body shape, and you should never use your genes as a crutch or an excuse not to take care of yourself. Remember:

1. You cannot control your unique genetic makeup, your body type, your bone structure, your tendency to store fat in certain places vs. others or which "light switches" you are born with.

2. You do have some control over how your genes express themselves based on your lifestyle and how well you take care of yourself.

3. Because your lifestyle is what you have control over, focusing on that—as opposed to wallowing in misery over your "bad" genes—is what is most important.
So how exactly do you best take care of yourself?  These quick tips work for everyone, no matter what your body shape is (or what you hope it becomes):

1. Eat real food 90% of the time. This means whole, unprocessed food that is as close to its natural state as possible. A healthy amount of real food can do wonders for your body.

2. Lift heavy things 2-3 times a week. Strength training is important for many reasons, especially for women. Lift weights for joint health, stronger bones and better posture, as well as the maintenance of your muscle mass and overall confidence.

3. Walk for leisure often. Walking is a fantastic low-level exercise that can aid in recovery, improve your sleep and help you relax and de-stress. Getting more active each day can help you turn off genes that encourage you to store fat.

4. Find ways to manage your stress. Stress is an absolute killer, and if you don't mange yours properly, you are opening yourself up to a host of health issues. It's also been linked to increased fat storage in the body. Find ways to manage stress effectively, whether it's going for a walk, getting a massage, or having positive interactions with friends and family. In short, take a few minutes each week to take care of YOU.

5. Get quality sleep. Lack of sleep is another big health problem, because when we aren't sleeping well, our bodies aren't repairing the damage we did to ourselves during the day and we sure as heck aren't recovering from our workouts. Shoot for 7-9 hours a night in a cold, dark room, and do your best to hit the sack before 11 p.m.

6. Love yourself. Stop comparing your body to other people and start embracing your unique size and shape. Variety is the spice of life! Be grateful for all the things your body can do. Remember: You are more than a body or a number on a scale. 

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LEER95621 8/27/2020
My mother always told my sister and I were built like linebackers our shoulders are so wide and we broke up really easily they’re just buy a normal work I carry a load of paper I worked at the yogurt shop moving half gallons of yogurt six days a week I became a float full back. My mothers brothers girls are built exactly the same way and they could never figure out why they never look like their mother side of the family until they saw me and went oh that’s where it comes from jeans and Heather expressed are a crapshoot Report
CECELW 6/14/2020
Yes....I've heard about this years ago Report
NENEBFIT 3/22/2020
Fascinating article, thank you! I think that the BMI charts should take into consideration some of this info. For a naturally curvy woman to be expected to have the same BMI as a naturally straight figured woman is frustrating to me. Report
KHALIA2 12/2/2019
Thanks for sharing! Report
KHALIA2 12/2/2019
Excellent Article! Great info! Thanks for sharing this one! Report
SHOAPIE 11/1/2019
Thanks Report
I have always been pear shaped, but now that I am older it’s probably more avocado.....I always thought it was because I have short heavy legs. I have a long body and I did have an hourglass shape figure back in my twenties and teen years, but never a six pack.....since my first pregnancy I have been seriously battling with my weight. Report
My father's athletic build and physical talents weren't the only predisposition I inherited. Alcoholism, impulsivity, and emotional sensitivity, too. The later have impacted my life and my body more, but I'm finally in a good place with issues, which shows up as a healthy strong body. Report
Excellent information! Report
Thanks! Report
Great amount of info in your article. Would be nice to have some info for those of us over the age of 60 (and who have had multiple pregnancies) because everything slows down and the body sags as we age and what works in a persons 20s or 30s is not the same for the 60s or 70s.
Thank you. Report
thank you for sharing
Great info! Thanks! Report
Very interesting article Report
Pleased you were able to find a happy middle ground. Report
Thanks for sharing Report
Great info! Report
Excellent! Thank you so much for sharing this information! Report
Interesting article Report
Thanks for sharing Report
Great article lots of infomation Report
Very interesting, Thanks! Report
I love this article!

At 14 yrs old, I was 5'6" tall and crept up to 110 lbs. One of my aunts commented that I was getting fat...but that I wasn't going to do that anyway because, "just look around at us!" Sadly, my teenage mind panicked and I starved myself down to 89 lbs. BUT...I give her credit for lighting the fire under me that said "I'll NEVER accept that!" After having children, I was bigger than I wanted to be. Did I just accept that was my lot in life? No! I started working out, watching what I ate, etc. It took a long time, and finally finding out so many foods were making me sick, but I never gave up fighting against accepting what she said. Report
Great article. Gets one thinking. Report
Well, all of this is informative-- Report
Never get older. Never go full menopausal. Never injure yourself.

Sorry, but you're naturally super-thin, Miss Guest Blogger. And while I'm cool with you realizing that extreme dieting stinks and causes your body to rebel, guess what? It also does that if you lose over 100 pounds.

Even if you have to lose over 100 pounds.

Spark really has no idea what to do with extreme weight losers after we've done it one time. Because we inevitably ricochet back. And then what? Our caloric needs are far, far less.

I am, no lie, at a point (see the study of the people who were on The Biggest Loser) where I would have to skip dinner every day, for the rest of my life.

In order to maintain, not lose.

And I am in my fifties. I am not at death's door. And I don't want to be. But cheerleading to just walk another 1000 steps or taste that yummy celery and pretend it's chocolate cake (or even a regular, normal salad, yes, really) are just so much noise.

And my doctor and a dietician are having trouble figuring it all out, too.

So riddle me this, Batman (because I absolutely do NOT want surgery): how am I supposed to magically transform into a fat burner again, when I can't run, can't walk for distance, have been told to stop lifting because muscle is heavy, and I already eat low carb?

But hey, tell us again about all the different ways you look in a bikini. Report
I always thought I was medium boned and hippy (like my grandmother). Imagine my surprise to lose 85 lbs and added exercise to find that I am small framed and have no hips! Report
Thanks for sharing I learned some things. Report
When I was heavier, I used to consider myself big boned. At 180 lbs, my ribs and clavicles started poking out on a 5'6" frame. At 155 lbs, my brother called my clavicles "soup bowls", even though the bmi chart says I'm right at overweight. I wish more people doctors and others emphasized the complicated numbers on the scale. The description is not one-size-fit all, and also, fighting against nature is really difficult. If some folks get down to the best recommended weight for their heigth, they look horrible. There's weight in my legs (size 4-6), but my upper body is leaner (size 4). Good article. Report
Everyone has a six-pack, just most of us carry it around in a soft sided carrier! Report
Great info, this gives me hope!
goooood Report
I'm a hybrid; mostly an endomorph, but I have a definite (even exaggerated) hourglass figure. My breasts and hips are very large (overly so for my short stature), but my waist is small in comparison. I also am somewhere between endomorph and mesomorph in terms of weight gain. I generally only gain when I overeat, but there are times when it comes on fast. Stress is definitely my biggest obstacle to overcome. And I know that I need to let go of some of my unrealistic expectations (talking to you, large thighs and butt), but this kind of hit it home for me. So I'll try to start loving the extra junk in the trunk. Report
I am apple shaped with very defined legs, (people always stop me and ask me if I work out my legs in particular) I tell them sure why worry about my round belly! lol I also have broad shoulders. I always tend to lose weight in my butt and legs first. I wasn't happy to read that the stomach will be the last place that I will lose the weight, but I know not to give up! Report
I am 25% mesomorph and 75% endomorph. I only put on weight if I over eat or am severly constipated. I have IBS -C. I have broad shoulders and an hourglass figure but tend to gain weight in my lower belly, inner thighs and buttocks. Report
thank you for an informative article, one thing I have found as an "apple" is if I work on upper and lower body for muscle and definition my tummy looks smaller! I may never have a 6 pack but I can focus on toning overall to look balanced. Report
My trainer says I am a mesomorph....which probably explains why I wore (at my smallest) size 6-8 jeans and weighed 180 for most of my life until menopause, etc. Right now, I look like a Russian weight lifter (male) with a big stomach! Nice for a man, but not so hot for a woman! I loved this article because it just reaffirms the idea (after having cancer) that you must "go with what you've got," and enjoy your life while you have it. The scrawniest little people look at me weird at the pool, but most have something quite obviously not the best on their own bodies! Get over it and let's be kind to one another, OK? Report
I'm primarily a "pear" and I always had trouble with jeans; when they fit my butt, the waist gapped. I've gained a lot of weight since my best physical self, and I'm trying to remedy that. I'd like to have my "six pack" again. Thanks for the compassionate article. Report
Thank you for putting yourself out there, nice to hear it's not all wonderful being uber fit. Report
Thank you for the much needed reminder. Report
I'm not a scientist or pro anything, just a gal. I've been saying this for several years now and no one believes me accept my husband who has studied this in college. I'll admit, it's depressing to have my thoughts confirmed but a relief at the same time. I wish more doctors knew/believed this, it would make life a lot less stressful. I'm a combo Endo-Meso. Even when I was thinner I wasn't thinner, if you know what I mean. My weight gain was due to hormones I was put on for many years, which now I'm off and trying to get the weight off. I accepted my build (not meaning fat amount) years ago, I wish others could too. Report
"There are three generally accepted body types: ectomorph, mesomorph and endomorph."

This is not science! This concept was debunked YEARS ago! While genetics most likely plays a part in your ability to gain and lose weight, the idea that there are body "types" is left over junk science from the age of Eugenics. Report
Thank you for this. It's a good perspective to have. Report
Love the article. Just starting out on my journey again. Hopefully I will finally get off the weight roller coaster and find health. I love your curvy look by the way. Report
Thank you for this article. After 10 months, I have lost 52 pounds, and am having trouble deciding when to stop losing and go into maintenance mode. I had a Microfit health assessment in July and another in November, and in the November reassessment, they told me that my body fat had dropped to 19.6, and I didn't need to lose any more weight. However, I tried to push on to lose more weight, hoping that the extra fat around my waist would go away. Then my dermatologist told me that losing more weight would not make that fat go away, and she advised me to stop losing weight. I think it is time to accept that this is my new ideal weight, about 15 pounds heavier than I was as a young woman. Every indicator on the Microfit assessment was in the excellent category, except BMI, which is only fair, but I think that is naturally high in me because I do have big, heavy bones, and I have done lots of strength training and cardio. It is hard to know what the right weight is for me at this age. But when I take into account all factors, including my new clothing size and the compliments that people bestow on me, my body type (Mesomorph, hourglass) and my energy level, then the weight where I am now seems about right. Thank you for pointing out that my 'perfect' weight is unique and I don't have to strive for some magic number that may not be realistic for me. Report
Love the article it is so on. I am a yoga teacher who studied Ayurveda medicine and learned my body type was not what I thought. When I listen to my body I do great. I have not listened for a while but your article is making me take a 2nd look as to why my weight loss has stalled and I have developed Type 2 diabetes. This will make me re think my diet choices again. Thanks Report
HI Molly, I am a scientist who has spent the last 30 years studying gene-environment interplay and I want to congratulate you on the way you describe genetic contributions to body type and how gene expression is our bodies response to the environment (how we treat our bodies). Your description is right on. Our genes are listening to the environment and they respond accordingly. And yes, the idea of a nature-nurture dichotomy is dead. I have rarely read a popular article that gets the relationship between genes and the environment correct. Well done Molly this is not an easy concept to convey and you nailed it. Made my day reading this article.
I love your posts Molly. I think I am a very slim endomorph, which its no wonder I have to eat like an angel and work out like the devil to lose. But I have, its hard but I have been patient. I was also wondering why I still have a little bit of belly fat even though I am pretty slim everywhere else. Dang body types. I think more weight training and more patience and I'll eventually have a flat stomach, but even if I don't, more weight training will make me strong and boost my resting metabolism. Thanks for a another great article. Report
I am an ex-fitness trainer and was always very fit for my body type due to strength training. What surprised me was just HOW much harder it is to keep weight off during peri- & menopause (I went through it in my mid-40's). Previously I could stay below 120# easily with healthy exercise & diet. That's a good weight for someone 5'4". Now A similar diet with the same amount of strength & cardio doesn't get me much below 138#. I am still not as heavy and much more healthy overall but am following the aging trends of my family. As a trainer, I may have discounted this phenomenon with my older clients a bit too much. Report