Healthy vs Skinny: The Truth Between Low Body Fat and Health

When I was about 14, I had my own idea of what being healthy meant. I saw an image of a woman on an online fitness ad holding hand weights in front of a gym mirror. She was lean; lean arms, lean legs, lean calves, lean neck, and a LONG and LEAN abdomen with obliques. She looked so skinny and shredded. You can picture her now, a model. As a young girl, I saw her and I thought that was the goal to strive for. She looks amazing, she probably eats salads and fruit smoothies all the time. And I wanted to look like her, because that was “healthy”. 

I thought healthy and skinny were just different words meaning the same thing. And if everyone does just the right amount of cardio and eats salad and low fat and low carb, then everyone would be skinny and healthy. Low calorie was healthy. Low carb was healthy. Low fat was healthy. Being skinny was healthy. 

But the truth is, being healthy and being skinny is not the same thing. And photoshop is real. And so are eating disorders. 

After all these years of eating, not eating, running, CrossFit, bodybuilding, and martial arts, I learned a lot about health and wellness and fitness. And here is the simple honest to goodness truth everyone serious in the fitness industry knows:

Skinny does not mean healthy and healthy does not mean skinny.

So why are they associated with each other? Why are they often seen as interchangeable in everyday conversation? Where does this mix up happen? Does this mean 6 pack abs showing is not healthy? Does this mean eating healthy foods will make me fat? Let’s clear the air a bit.

So having lower body fat is technically healthier for you than higher body fat. This is what we call in the science world “correlation” (i.e. the relationship between two different variables or things).  Research consistently shows that maintaining lower body fat percentages is associated with lower risk for “all-cause mortality” (including but not limited to cardiovascular disease, diabetes, and stroke). 

Now here is the kicker. This systematic review (review of a bunch of other top tier research papers) does NOT reveal a linear graph. It actually shows more of a “J” shape. The numbers show a more complex story. The research statistics show that having a body fat percentage below 20% for men and below 30% for women is ALSO associated with a higher risk for all-cause mortality. (see Disclaimer #1) So in short, too skinny is bad and too fat is bad. Go figure. 

Figure showing Dose-response association of body fat percentage with the risk of all-cause mortality in women.

Figure showing Dose-response association of body fat percentage with the risk of all-cause mortality in men. 

So, what does that mean? It appears that there is more to play than just how much body fat you have on your body when it comes to being considered “healthy”. And I can talk all day about this kind of stuff, but let's break it down to some real basic science. Being healthy does include having a low-ish body fat percentage, but also includes two other relevant variables:

1. Lean body mass

2. Distribution of Fat

   
   

Let's dive into lean body mass. Lean body mass is basically how much mass you have on your body that is NOT fat. Basically, the mass of your muscle, bones, organs, and even water in your body. Obviously, we have no conscious control over how much our organs or bones weigh, but we do have the ability to grow muscle mass. In fact, lean muscle mass is closely associated with lower risks for disease like Type 2 diabetes. So having a bit more muscle is healthier for you than a bit less. And we know for a fact that people with more muscle tend to have lower body fat percentages due to lifestyle factors and burning more calories at rest. So that is that. 

Now let's switch over to the topic of the distribution of body fat. Wanna know why women are shaped like “pears” and men tend to be more like “apples”? Why do women eat food and it “goes to our hips” while men tend to get a “beer belly” when they do the same? It is all about genetics and hormones, as estrogen and testosterone are found to affect how fats are absorbed, created, and stored in the body. The fat stored around our internal organs is called our “visceral fat”, and high amounts are correlated with a higher risk for mortality than subcutaneous fat (the fat just under our skin, what makes us have cellulite or have a “belly pooch”) This may leave you wondering why men aren’t at a higher risk for mortality than women, since most of their fat is on their belly. This often is due to, ding ding, higher muscle mass (mentioned in Lean Body Mass paragraph), which men seem to often have more of than women. This is also why women can get away with having a little less muscle than men and more fat when younger, because we tend to carry less in our belly area and more in our breasts, hips, and thighs. Hint: hormones are ALSO the reason why women tend to get more of a belly when they get older and hit menopause, as they tend to have less estrogen, therefore more fat storage diverted from hips to the belly. Unfortunately, women tend to also lose what little muscle we do have during this time as well, making it a double whammy for fat gain and increased incidence of metabolism problems. So, it's not just about how much fat but also where the fat is found. 

The human body is not designed to starve and live life to the leanest. It is also not designed to haul around extra weight all the time. There needs to be a balance. Skinny simply means low body fat, but it doesn't give you a good picture of the overall health of the individual. And health is so much more than a number on a scale or looking “toned” and “lean”. It's about taking care of yourself as a functioning human. It is about eating enough nutrients to fuel your body and moving your body to help it stay mobile and strong. All in all, treat your body well, and it will treat you well in return. Aim to be healthy, and leave being skinny and perfect looking to the photoshop models. 

Disclaimer #1 : Don't let the 25% rule for men and 30% rule for women scare you too much. You might be leaner than that or slightly above that. That's ok, it doesn’t mean you are going to face a certain painful death. These numbers are for the general adult population. It does not factor in those who have more lean muscle mass with their lower body fat %, it only factors in the average population of adults. The key is to follow up with your doctor to make sure your health indicators are where they need to be to find what body fat percent is healthy for you. 

Disclaimer #2: Furthermore, the two variables mentioned in this post are not exclusive of other variables. These two are mentioned because a) they hold very high clinical relevance and have been extensively researched and b) the variables needed to be condensed for concern of the post's length. 

Citations:

Jayedi, A., Khan, T.A., Aune, D. et al. Body fat and risk of all-cause mortality: a systematic review and dose-response meta-analysis of prospective cohort studies. Int J Obes 46, 1573–1581 (2022). https://doi.org/10.1038/s41366-022-01165-5

Nauli, A. M., & Matin, S. (2019, December 5). Why do men accumulate abdominal visceral fat?. Frontiers in physiology. https://pmc.ncbi.nlm.nih.gov/articles/PMC6906176/#S2 

Haines, M.S., Leong, A., Porneala, B.C. et al. Association between muscle mass and diabetes prevalence independent of body fat distribution in adults under 50 years old. Nutr. Diabetes 12, 29 (2022). https://doi.org/10.1038/s41387-022-00204-4