Body Composition

Many of us use body weight or BMI (body mass index) for a quick approximation of our health status. Yet the utility of these metrics is limited because they provide little information about a far more relevant parameter: body composition – and in particular, body fat and its distribution. Body weight and BMI alone do not discriminate between muscle mass (which we want to maintain or increase to promote longevity) and fat mass (which we generally want to keep relatively low). Thus, when we set a goal to “lose weight,” our real aim ought to be losing fat.

Losing fat mass isn’t necessarily easy, but unfortunately, that struggle pales in comparison to the challenge of keeping it off. This is caused in large part by a hormone called leptin, which is secreted by fat cells and plays a critical role in numerous endocrine pathways and functions, including the regulation of energy homeostasis. Leptin is secreted at levels proportional to body fat and acts as a “satiety hormone” in the brain, causing a reduction in food intake. However, as leptin signaling decreases – due to fat loss or to key neurons becoming leptin-resistant – the brain interprets this as a sign of starvation, and drives increased appetite and reduced energy expenditure to counteract the loss.

The content selections below provide more information on the accumulation and measurement of body fat, different types of fat and their relative impacts on health, and the effects of leptin on appetite and metabolism.

#194 – How fructose drives metabolic disease | Rick Johnson, M.D.

Fructose turns out to have been meant to be this wonderful system for survival, but in our culture with the amount of sugar in foods that we are eating (that either provide sugar or can be turned into fructose), this pathway has become hazardous.” —Rick Johnson

#167 – Gary Taubes: Bad science and challenging the conventional wisdom of obesity

Doing a background analysis is the hard, relentless, rigorous grunt work of science. It’s endless and thankless, because if you do it right, all you’ll do is prove that you were wrong all along.” —Gary Taubes

#157 – AMA #22: Losing fat and gaining fat: the lessons of fat flux

“If we didn’t understand fat flux, there would be no flux capacitor and Marty might still actually be in the past.” —Peter Attia

#136 – AMA #17: Body composition methods tour de force, insulin resistance, and Topo Chico

“Skeletal muscles are the greatest reservoir that you have for glucose disposal.” —Peter Attia

#120 – AMA with Dom D’Agostino, Ph.D., Part II of II: Ketosis for cancer and chronic disease, hyperbaric oxygen therapy, and the effect of ketosis on female health

“The function of the mitochondria and mitochondrial health are the ultimate mitigator of neurodegenerative diseases…just by reducing the potential for reactive oxygen species related damage.” — Dom D’Agostino

#69 – Ronesh Sinha, M.D.: Insights into the manifestation of metabolic disease in a patient population predisposed to metabolic syndrome, and what it teaches us more broadly

“The way we raise our kids early on might actually set a pattern for how much of an accelerated life, or how much of a stressed out nervous system they might have later on. . . a lot of the behavioral patterns that we’re instilling in our kids are kind of setting the foundation for insulin resistance and inflammation early on.” —Ronesh Sinha

#33 – Rudy Leibel, M.D.: Finding the obesity gene and discovering leptin

“I’ve always felt that it was really somehow an enormous opportunity and a gift to be able to pursue this down to the level that I’ve been able to do in the past 30 years.” —Rudy Leibel

How to make a fat cell less not thin: the lessons of fat flux

Does being in ketosis automatically translate to fat loss?

Good science, bad interpretation

In 2012, the Journal of the American Medical Association (JAMA) published a study entitled Effects of Dietary Composition on Energy Expenditure During…

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