What’s your best body fat?

This is probably the most common thing a coach hears from a new client:

I want to lose weight.

If they’re athletic, or understand the difference between muscle and fat, perhaps that client might say:

I want to get leaner.

Whether male or female, newbie or veteran, the vast majority of coaching clients — indeed, the vast majority of people in the world in the 21st century — are chasing the dream of being skinner, smaller, and/or leaner.

What’s “natural”?

Now, some folks like to say that any attempt at getting skinnier, smaller, and/or leaner is selling out — it shows that we’ve all been suckered by The Anti-Fat Conspiracy / Beauty Myth into shrinking and shaming our natural, beauteous, abundant, fleshy exuberance.

This argument forgets that almost nothing about our current environment is “natural”, so it’s very hard for our bodies to know what the hell “natural” is, never mind to find it effortlessly.

However, if we’d like to talk about what’s “natural”, here are some data about the Body Mass Index (BMI) from a few foraging (hunter-gatherer) and subsistence agriculture societies.

(Or, in the case of some groups, data from when they were living in hunter-gatherer groups, even if they aren’t any more.)

Of course, all organisms somehow modify their environment. “Natural” is an imaginary idea.

But we could factually say that humans spent most of their evolutionary history in conditions that are not the conditions most of us live in now. So these folks live as close to “natural” as one could realistically expect:

  • spending their time mostly outside;
  • foraging for their own food (or growing very small plots of it, just enough to live on);
  • eating “close to the ground” — everything fresh-picked, fresh-caught, fresh-dug and almost entirely unprocessed; and
  • doing a lot of physical activity every day.

Guess what: People in these groups are, or were, relatively lean. Shocker.

Selected hunter-gatherer (HG) and subsistence agriculture (SA) populations, by sex and BMI

Location Population Activity Sex BMI
Namibia !Kung San HG M 19.4
F 19.1
Kavango SA M 19.4
F 20.3
Cameroon Pygmy HG M and F 19.9-20.9
Australia Aboriginal HG M and F <20
Kenya Ariaal HG and SA M and F 17.8
Ethiopia Elka / Oromo SA M 19.7
F 20

Table source: Speakman, John. A nonadaptive scenario explaining the genetic predisposition to obesity: The “predation release” hypothesis. Cell Metabolism 6 (July 2007) 5-12.

How to understand BMI

  • <19: Underweight
  • 19-24: Normal
  • 25-29: Overweight
  • 30-39: Obese
  • 40+: Extremely obese

For instance, among the !Kung, women have an average BMI of 19.1.

To put this in understandable terms, at a BMI of 19.1:

  • A 5’1″ woman would weigh 101 pounds.
  • A 5’4″ woman would weigh 111 pounds.
  • A 5’7″ woman would weigh 122 pounds.
  • A 5’11” woman would weigh 137 pounds.

For comparison, in the United States, according to the Centers for Disease Control, the average adult man currently has a BMI of 28.5 and the average adult woman has a BMI of 28.3.

This means that at a BMI of 28.3:

  • A 5’1″ woman would weigh 150 pounds.
  • A 5’4″ woman would weigh 165 pounds.
  • A 5’7″ woman would weigh 181 pounds.
  • A 5’11” woman would weigh 203 pounds.

Now, I’m not saying this is good or bad. BMI is not a marker of health or anything other than just what weight someone is relative to their height.

I’m not saying everyone falls into this average. Humans are diverse, and even in a small group there is variation.

I’m just saying this is how it is, on average, in these groups, under these conditions.

If we’re making the argument that some bodies are more “natural” than others, we have to compare apples to apples.

And the apples tell us that under “natural” conditions with particular requirements and limitations, there is probably an optimal range of weight and body fat to have.

What’s “optimal”?

As I like to say, biology is all about sweet spots and trade-offs.

Everything is a compromise in biology. Every advantage has a corresponding downside.

There’s no one “best” thing to do. There’s no “best” way to be.

However, there are better and worse solutions to problems. There are optimal ranges for everything.

If we think about body fat, and how it works, you can see the reasons why there might be an optimal range for it.

As a chemical factory, fat secretes important hormones and cell signals.

  • Too little fat and that hormone production switches off. No sexytime or babymaking. The low body fat levels tell the brain — via chemical messengers — “Shit, we’re starving!” And/or the immune system can’t do its job: we get sick easily and our energy levels drop.
  • Too much fat and we make too much of those hormones and cell signals. Our metabolisms and reproductive systems get disrupted. Inflammation goes up.

As a body tissue, fat cushions us.

  • Too little fat and we’re often bruised and uncomfortable. Our internal organs smash together.
  • Too much fat and we can’t move well or quickly. Our internal organs get compressed, and/or fat goes where it shouldn’t, such as marbling into our livers or our kidneys.

So we need enough body fat to store energy and ensure the right chemical balance, but not so much that we’re slow and stiff, or that our chemistry is disrupted.

As with fat, weight and size has a sweet spot too.

  • Too small / thin, and you may become too vulnerable and frail (though as the case of Homo floresiensis suggests, some hominins may have been able to survive this way).
  • Too big / dense, and your resource and energy demands become too great, plus you overload the joints and skeletal structure.

This means that:

  • Some people might function and feel better if they lost body fat and/or weight.
  • Some people might function and feel better if they gained body fat and/or weight.
  • Some people should just carry on as-is. Way to go, happy mediums! Look at you optimizing!

So changing your body fat and weight is not selling out, or being a sucker for Big Diet. It may be a very logical and well-founded strategy for improving your health, physical function, longevity, mobility, and/or athletic performance.

Importantly: That optimal range does not involve looking like a magazine cover.

In fact, that magazine cover model may not be in their optimal range for function, performance, health… or sanity.


What’s “realistic”?

Unfortunately, data show that folks who might benefit the most from reducing their body fat a little bit often have the most unrealistic expectations.

In other words, if you walk into a weight-loss coaching scenario at 300 lb, you may want to be 120 lb of shredded steak, rather than, perhaps, a 250-lb person who feels much better.

So when you get to 250 lb (if you do, because you might even give up before that point), you’ll feel like a failure, because it’s not what you imagined.

The data also show that if excess fat tissue is causing mechanical or metabolic problems for you, you’ll probably feel and function better even if you only lose 5-10% of that weight.

In other words:

  • If you’re an unhealthy 300 lb person, you can become a healthier 270 lb person. Or even a healthier 285 lb person.
  • If you’re an unhealthy 200 lb person, you can become a healthier 180 lb person. Or even a healthier 190 lb person.

You can also become a healthier person who weighs the same but changes their proportion of lean muscle tissue to body fat.

So if you start out as a 200 lb couch potato and, a few years later, win the heavyweight powerlifting championships one weekend plus the Clydesdale division of a 5K the weekend afterwards, you’ve probably dramatically improved the way you feel and function.

What’s “desirable”?

Here, I’m talking about what’s desirable for function, performance, and health, not desirable from a “hubba hubba” perspective.

What’s desirable in terms of body fat is:

  • What allows your body to do its job — to produce what it should produce, in the amounts it should be producing it
  • What allows you to move freely and well, with no limitations because of size or adiposity
  • What allows you to feel good at a deep level — about who you are, how you are, and what you’re doing
  • What allows you to be the kind of person you truly want to be, living a life that is rich, expansive, and full

As someone who’s been everything from very lean to very over-fat (and whose BMI currently hovers on the border of “overweight”), I can tell you that leanness ain’t all it’s cracked up to be… but carrying a lot of extra body fat doesn’t feel great either.

When I was too lean, my hormones went AWOL and I turned into a crazy, anxious no-period-having bitch.

When I was too over-fat, everything hurt and I felt shitty.

Now, hanging out on the border of “overweight”, I feel happy and healthy. Nobody wants to take my picture in a bikini. But I’m a whole lot less nuts, and my doctor is high-fiving me.

What this means for you

You never, ever have to get “ripped” to be healthy.

In fact, stop focusing so damn much on how you look. Look at your feelings and function.

  • How are your metabolic markers?
  • How agile and mobile are you? Can you get around, tap-dance through an obstacle course, or run for the bus?
  • How is your athletic performance? Can you do what you want to do, as well as possible?
  • How do you nourish and treat your body every day? Are you consistently giving it good food, lots of fun activity, and love?

What you DO have to do is what those foragers do.

  • Get plenty of activity every day, throughout the day.
  • Get outside, engage with your surroundings, and get natural cycles of light and dark.
  • Get lots of sleep and stay relatively chilled out.
  • Eat a variety of fresh foods.
  • Stay connected to a vibrant community that supports you.

If you do this consistently and well, then your body will very likely find its happy place — whatever that is.

And you’ll feel like a natural woman.