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.

Body Composition

Visceral Fat vs. Subcutaneous Fat — What’s the Difference?

This clip is from “Ask Me Anything” (AMA) episode #17, originally released on November 9, 2020. If you’re a member, you…

Body composition: impact on disease risk and how to assess and improve it

A refresher on why you should care about body composition and a practical guide to determining and interpreting your measurements

Is a recent clinical trial enough to support the use of semaglutide in treating adolescent obesity?

The imperative for effective weight management strategies in children and teens is clear, but in our desperation for effective obesity treatments, are we allowing ourselves to be too shortsighted on testing?

To reduce appetite, skip late-night snacks

Two recent randomized trials found that biasing food intake toward the end of the day increases appetite and may reduce energy expenditure.

#227 – AMA #40: Body composition, protein, time-restricted feeding, fasting, DEXA scans, and more

“We don’t want to be consuming protein for energy purposes at all. We want to be consuming protein for muscle protein synthesis.” —Peter Attia

Different effects of fat- vs. carbohydrate-restriction on neural reward signaling

“A calorie is a calorie” seems like a simple and obvious statement. But do different macronutrients vary in their ability to drive obesity? A recent study by Dr. Kevin Hall and colleagues provides new clues – and likely new fodder for debate.

#212 – The neuroscience of obesity | Stephan Guyenet, Ph.D.

This system works better at protecting against fat loss than it does against fat gain.” —Stephan Guyenet

#205 – Energy balance, nutrition, & building muscle | Layne Norton, Ph.D. (Pt.2)

Lean body mass is inversely proportional to your risk of mortality after age 50.” —Layne Norton

Should BMI be used? Measuring obesity at the individual level

This video clip is taken from  Podcast #197 — The science of obesity & how to improve nutritional epidemiology with David…

Why is maintaining weight loss more challenging than losing weight?

This video clip is taken from Podcast #197 — The science of obesity & how to improve nutritional epidemiology with David…

#197 – The science of obesity & how to improve nutritional epidemiology | David Allison, Ph.D.

How much does obesity kill you because it stigmatizes you and it creates some stress?”  —David Allison

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