Body Fat: Health Dangers of Being Too Fat or Too Lean

by Nils Osmar. Nov. 6, 2022. Medical Disclaimer

Having a high level of body fat can be detrimental to our health. But so can having too little fat.

According to this Harvard Health article (Abdominal obesity and your health), excess body fat (particularly in our abdominal area) contributes to major causes of death and disability, including:

  • heart attacks and cardiovascular disease
  • strokes
  • high blood pressure
  • cancer
  • diabetes
  • osteoarthritis
  • fatty liver
  • depression
  • and many other health conditions

Obesity is also associated with a reduced life expectancy, partly because obese individuals are at greater risk of succumbing to the health problems listed above.

Too little fat

The same is true of having levels that are too low. According to this Healthline article (6 Health Risks of Being Underweight), risk of being too lean include:

  • malnutrition, vitamin deficiencies, or anemia
  • osteoporosis from too little vitamin D and calcium
  • decreased immune function
  • increased risk for complications from surgery
  • fertility issues caused by irregular menstrual cycles
  • growth and development issues, especially in children and teenagers

According to this article, having too low body fat is associated with decreased life expectancy (after we pass a certain age).

So what’s best for health (and longevity)?

The short answer is, it depends.

According to an American Journal of Clinical Nutrition study, what constitutes an ideal percentage of body fat (in terms of health) varies according to both age and gender. Women have a naturally higher body fat percentage than men. 

Possible healthy ranges might be:

  • Ages 20 to 39: for women: 21% to 32%. 
  • Ages 20 to 30: for men: 8% to 19%. 
  • Ages 40 to 59: for women: 23% to 33% 
  • Ages 40 to 59: for men: 11% to 21%. 
  • Ages 60 to 79: for women:  24% to 35% 
  • Ages 60 to 79: for men:  13% to 24%.

This Medical News Today article has comprehensive charts in more detail for both sexes.

The takeaway

The takeaway (for me) is that what was healthy in our 20s may not be when we’re in our 60s or 70s. For people in the anti-aging, pro-longevity communities, there may be some unanswered questions, though. One is whether the “ages” in the above recommendations correlate best with our chronological or biological ages.

There’s some evidence, for example, that if we follow an effective anti-aging protocol, our epigenetic age may be 20 or 30 years lower than our number of birthdays. If we’re chronologically 50 years old, but biologically in our early 30s, which age category would apply? I don’t have an answer, but it’s the sort of question that we’ll be needing to address if we succeed in reversing aging.

My situation

I weighed 142 pounds when I was in my twenties; I literally couldn’t gain weight no matter how much, or what, I ate. I tried taking swimming classes during that period, but was so skinny that I sank like a stone when I went to the pool. I had too little fat to stay bouyant.

This changed when I was in my forties (though I hadn’t made any changes in my diet or level of exercise). The idea that our metabolism changes as we age is often said to be a myth, but speaking anecdotally, my experience would suggest that in some cases at least, it may be true.

Since that time my body weight has fluctuated, tending to drift upward when I eat more calories or carbohydrates such as grains, and drop when I eat less. It also tends to climb when I eat dairy, even so-called “healthy” dairy products sutrch as kefir and yogurt, and to drop when I do more fasting.

Based on the charts, I’m fine “for my age” but would be a few pounds overweight if I were in my 30s. I wonder sometimes if I should let myself gain a few more pounds, since what’s healthy for a 40 year old isn’t necessarily ideal for a 69 year old. So I can’t say I have it completely solved. I am trying to be proactive against sarcopenia, so my main focus is on eating healthy, high nutrient foods and both getting enough healthy fat to support my brain, and enough protein to support muscle growth.

Shaming and celebrating obesity

There’s a history in our culture of ridiculing and shaming people who are fat, which is obviously problematic. Anyone can find themselves gaining excess body fat; shaming and judging people in this situation doesn’t help.

The problems caused by fat shaming have caused a reaction in some circles of declaring that “obesity is beautiful/fat is identity”; declaring that any discussion of the health dangers of obesity is “oppressive”; and, in the extremes, celebrating and promoting social media stars who are morbidly obese as “healthy”.

Both fat shaming and the celebration of morbid obesity, to my mind, are reflective of the same mentality; they’re flip sides of the same nonsensical coin. They’re also reflective, I think, of the bad advice obese people are given (essentially to starve themselves) which inevitably leads to more weight gain when the “dieting” ends.

In my experience, it is possible to lose excess body fat while gaining muscle and improving our overall health. But it can take a while for people to find an approach that works and supports, not only weight loss, but health. Alternating between fasting and feasting days worked for me; very different approaches may work for others.

Not medical advice

This article is not intended as, and should not be taken as, medical advice. I’m not advising that people eat any particular diet or take any particular supplements, just reporting on what I’m doing. All supplements can have side effects; I would encourage people to research both possible benefits and side effects before starting on any supplementation regimen.  See full Medical Disclaimer

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