Body Composition Over Body Weight: A HAES-Aligned, Medicine 3.0 Approach

TL;DR: BMI and the bathroom scale tell you almost nothing about your real health. What matters is body composition: how much muscle you carry, how much visceral fat is wrapped around your organs, and how well your metabolism handles food. We follow Health At Every Size (HAES) principles and use DEXA scans to measure what actually drives long-term outcomes.

Table of Contents

• Why BMI Misses the Point
• Why "Weight Loss" Can Backfire
• HAES in a Longevity Practice
• The Real Metrics: DEXA, ALM, and VAT
• Beyond BMI: A Better Toolbox
• Common Questions
• Deep Questions

Why BMI Misses the Point

Step on a scale and it gives you a number. That number tells you about your relationship with gravity. It tells you almost nothing about your health, your metabolism, or your long-term risk of disease. Most clinics still center care on BMI (Body Mass Index), a number from the 1830s that divides your weight by your height squared. BMI cannot tell apart a heavily muscled athlete, a sumo wrestler, and a sedentary office worker who looks slim but carries deep belly fat. They can all share the same BMI and have wildly different health. In Medicine 3.0, the model we follow at Fishtown Medicine, the more useful question is what your body is actually made of. We focus on tissue quality. We look at how much muscle you carry, how much inflammatory fat sits around your organs, and how your metabolism is performing. We are also HAES-aligned. HAES stands for Health At Every Size, a framework that respects body diversity and rejects shame-based medicine. Aligning with HAES does not mean ignoring biology. It means we focus on physiology, not aesthetics.

Why "Weight Loss" Can Backfire

When someone says, "I want to lose weight," biology hears: I want to be smaller. If you slash calories and rely on long, slow cardio, you will lose weight. But up to 50 percent of that weight can come from muscle, not fat. That is a problem.

The Sarcopenia Trap

• Sarcopenia is the loss of muscle mass that comes with aging or with poorly designed dieting. It strongly predicts frailty, falls, and earlier death.
• The yo-yo cycle: When people diet, they lose muscle and fat together. When they regain weight, which most people do, they regain mostly fat.
• The result: Same weight on the scale, less muscle, and a slower, less responsive metabolism.

We do not want simple weight loss. We want body recomposition, which means protecting every ounce of muscle while specifically reducing the harmful fat around the organs.

HAES in a Longevity Practice

Health At Every Size (HAES) is a clinical framework that values respect, autonomy, and data over body shaming. Three principles guide how we apply HAES at Fishtown Medicine.

1. Weight inclusivity: We accept and respect the natural diversity of body shapes and sizes. Body size by itself is not a diagnosis.
2. Health enhancement: We focus on biomarkers like blood pressure, lipids, fasting insulin, ApoB, and inflammatory markers, not the number on the scale.
3. Respectful care: We ask before weighing. If the number is a trigger, you do not have to see it. The scale is a tool, not a judge.

The Important Nuance: Visceral Fat

While we respect size, we cannot ignore one specific type of fat: visceral adipose tissue (VAT).

• Subcutaneous fat is the fat just under your skin (thighs, hips, arms). It is largely cosmetic and genetic and is metabolically quiet.
• Visceral fat is the fat wrapped around your liver, pancreas, and gut. It behaves like an active hormone-producing organ. It releases inflammatory signaling molecules called cytokines (such as IL-6 and TNF-alpha) that drive heart disease, type 2 diabetes, several cancers, and dementia risk.

We target visceral fat because it is biologically harmful, not because of how it looks.

The Real Metrics: DEXA, ALM, and VAT

Instead of guessing with a bathroom scale, we use DEXA scans (dual-energy X-ray absorptiometry) as our source of truth. A DEXA scan uses a low dose of X-ray energy to map the bone, muscle, and fat in every region of your body.

1. Appendicular Lean Mass (ALM)

This is the muscle on your arms and legs. We compare it to your height (ALM Index, or ALMI).

• Goal: top 25 percent for your age and sex (75th percentile or above).
• Why it matters: Muscle acts like a sponge for blood sugar. The more muscle you carry, the more carbs you can eat without spiking insulin or glucose.

2. VAT (Visceral Adipose Tissue)

This is the inflammatory fat around your organs.

• Goal: generally less than about 1 to 2 pounds, depending on body frame.
• Strategy: VAT is unusually sensitive to sleep, stress, alcohol, and refined carbs. Improving any of those usually drops VAT before the scale moves.

Beyond BMI: A Better Toolbox

Metric	Tool	Goal
Visceral fat	DEXA scan	Less than about 1 to 2 lbs
Appendicular lean mass	DEXA (ALMI)	Above the 75th percentile
VO2 Max (cardio fitness)	Cardiopulmonary exercise test	Top 20 percent for age
Fasting insulin	Bloodwork	Under about 5 microIU/mL
ApoB	Bloodwork	Under 80 mg/dL (low risk)

Guidance from the Clinic

A common conversation in our practice:

"Dr. Ash, my old doctor told me I'm obese and need to lose 50 pounds."

My response is to step back and look at the data. Is your ApoB low? Is your fasting insulin sensitive? Is your blood pressure controlled? Are you strong? Is your VO2 max where it should be? If those answers are yes, your weight is much less important to your mortality risk than the BMI chart suggests. You may be what the literature calls "metabolically healthy" at a higher weight. If your fasting insulin is high or your VAT is elevated, we do step in. We intervene with nutrition (adding protein and fiber), training (resistance work), and sometimes medications like GLP-1 agonists when they are the right fit. We never intervene with shame.

Key Takeaways

• BMI is a poor health metric. It cannot tell muscle from fat or surface fat from organ fat.
• Muscle is medicine. Higher appendicular lean mass means a more resilient metabolism and a lower risk of falls and frailty.
• Visceral fat is the real problem. It is the inflammatory fat around your organs, not the fat on your thighs.
• HAES and longevity care fit together. We respect bodies and we still treat physiology that needs treatment.
• DEXA, fasting insulin, ApoB, and VO2 max beat the bathroom scale every time.

Scientific References

1. Spiegelman BM, Flier JS. Adipose tissue as an endocrine organ. Cell. Discusses how fat tissue secretes hormones and inflammatory signals.
2. Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006;84(3):475-482.
3. Keys A, et al. The Biology of Human Starvation (Minnesota Starvation Experiment). University of Minnesota Press; 1950. Foundational work on the limits of calorie restriction.
4. Kim TN, Choi KM. Sarcopenia: definition, epidemiology, and pathophysiology. J Bone Metab. 2013;20(1):1-10.

Medical Disclaimer: This resource provides clinical context for educational purposes. In the world of Precision Medicine, there is no "one size fits all", the right treatment plan must be matched to your unique lab work, physiology, and goals. Consult Dr. Ash to determine if this approach is right for you, especially if you have chronic health conditions or are taking prescription medications.