Does Being Skinny Fat Make My Metabolism Slow? – Question

Hey there, Dr. Skinny Fat. I am experiencing skinny fat and I’m pretty sure my metabolism is slow, or at least slowing down. I recently lost 11 pounds and my BMI is 22.9. But I still don’t like how my body looks. Losing weight and keeping it off has become increasingly difficult the older I get.

I admit that my diet, exercise, and lifestyle are not great. But I can’t say they really ever have been. So, why is it becoming harder now? Does metabolism slow as you age? I have friends who are not experiencing the same things as me. I thought that it was not until a person is much older than me (29) that metabolism starts to noticeably slow.

Which is why I am starting to think skinny fat is the culprit. Does being skinny fat slow metabolism?

Does Being Skinny Fat Make My Metabolism Slow? – Skinny Fat Question

Muscle is the engine that drives metabolism (1). It is genetic and highly heritable (2). The more muscle a person has, the stronger their metabolism. The less muscle a person has, the weaker their metabolism. Our research shows that skinny fat is deficient muscle tissue (3, 4, 5) that’s genetically influenced. With a BMI of 22.9, you are within “safe” — normal-weight –  BMI (18.5 to 24.99). Thus, by BMI definition (3), you are not experiencing excess body fat (regular white/yellow fat tissue).

But, when compared to what our research calls the baseline human body — the Standard Body Type One (BT1)(6) — there are strong indications that you don’t have all 600+ muscles fully developed. Our MRI Study (7) is working on validating things.

Your images indicate that you are experiencing skinny fat (lack of genetic muscle), likely on your upper legs, lower back, love handles, and stomach, no less. You mentioned that you are also experiencing it on your inner thighs, lower midriff, waist, hips, inner upper arms, and under arms.

When Does Metabolism Start to Slow?

The very latest research (8, 1) indicates that metabolism peaks as a baby, gradually declines until around 20 years old, and then levels out until around age 60. After that, it slows further by about 0.07% per year until death. So, at age 29, your metabolism has likely been relatively steady for a while. Of course, there are diverse things that affect metabolism (2), and it is possible that other variables are involved. Further testing by your doctor can help figure that out.

Diet, exercise, and lifesytle matter as well. If you aggressively starved (calorie deficit)(9) your body to lose weight, that can slow your metabolism (2), which can become permanent if done too long. A lack of exercise (10) — excess sedentariness — can also slow metabolism (2); so can too much exercise. Just as a poor lifestyle (11), including lack of quality sleep, too much stress, and a toxic environment, can negatively affect metabolism (2).

We developed the Scientific Health Quizzes to help you better understand your body composition (especially skinny fat), metabolism, diet, exercise, and lifestyle. The Scientific Body Type Quiz accurately estimates your unique body composition. The Scientific Metabolism Quiz accurately calculates your specific metabolism (slow, average, fast) and metabolic rate (decreased, steady, increased). The Scientific Diet, Exercise, and Lifestyle Quizzes are compliments that help paint a whole picture. Accounts are free, secure, private, and anonymous (depending on what info you choose to give). Free options are available.

References

1. Skinny Fat Science: How Skinny Fat Affects Metabolism, August 7, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/how-skinny-fat-affects-metabolism/
2. Skinny Fat Science: Is Muscle/Mass Genetic and How Does It Affect Skinny Fat?, November 20, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/is-muscle-mass-genetic-and-how-does-it-affect-skinny-fat/
3. Skinny Fat Science: What Is Skinny Fat?, July 26, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/what-is-skinny-fat/
4. Skinny Fat Science: Skinny Fat is a Lack of Genetic Muscle – Beyond Normal-Weight Obesity, August 13, 2025. https://skinnyfat.fellowone.com/skinny-fat-science/skinny-fat-is-a-lack-of-genetic-muscle-beyond-normal-weight-obesity/
5. Skinny Fat Science: Measuring Skinny Fat, July 22, 2026. https://skinnyfat.fellowone.com/skinny-fat-science/measuring-skinny-fat/
6. Britannica: human muscle system, Shane W. Cummings and Robin Huw Crompton (Fact-checked by the Editors of Encyclopaedia Britannica. https://www.britannica.com/science/human-muscle-system
7. Skinny Fat Science: Scientific Skinny Fat MRI Study – Proving What Skinny Fat Is, March 26, 2025. https://skinnyfat.fellowone.com/skinny-fat-science/scientific-skinny-fat-mri-study-proving-what-skinny-fat-is/
8. Duke Today: Metabolism Changes With Age, Just Not When You Might Think, August 12, 2021, Robin A. Smith. https://today.duke.edu/2021/08/metabolism-changes-age-just-not-when-you-might-think
9. Skinny Fat Science: The Best Skinny Fat Diet, According to Science, July 29, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/the-best-skinny-fat-diet-according-to-science/
10. Skinny Fat Science: The Best Skinny Fat Exercise, According to Science, August 2, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/the-best-skinny-fat-exercise-according-to-science/
11. Skinny Fat Science: The Best Skinny Fat Lifestyle, According to Science, August 14, 2024. https://skinnyfat.fellowone.com/skinny-fat-science/the-best-skinny-fat-lifestyle-according-to-science/