Thin but Prediabetic

"I am a 55 yr old who weighs 120 and has a HgA1C of 5.7%. I eat a healthy diet." · "I'm not overweight but my numbers are creeping."

This is more common than the public conversation about blood sugar suggests, and it's disorienting because every piece of advice you'll find assumes weight is the problem.

Why it happens at a normal weight

Visceral fat doesn't show on the scale. Fat stored around the organs is metabolically active and strongly associated with insulin resistance — and you can carry a meaningful amount at a normal BMI. Waist measurement catches what weight misses.

Low muscle mass. Muscle is the body's largest site of glucose disposal. Someone light but with little muscle has less capacity to absorb what they eat than the number on the scale suggests.

Genetics. Family history is a substantial independent risk factor. Some people are simply more predisposed, and certain ancestries carry higher risk at lower BMIs.

Age and menopause. Insulin sensitivity declines with age, and the shift in fat distribution after menopause happens at a stable weight.

Sleep and stress, both of which affect insulin sensitivity independent of body composition.

Why the standard advice doesn't fit

"Lose weight" is the default instruction and it's the wrong one here. There may be little to lose, and losing it could cost you muscle — which would make the underlying problem worse.

What to do instead

Build muscle. This is the main lever when weight isn't the issue. Resistance training twice a week, and enough protein to support it.

Protein at every meal. Twenty-five to thirty grams, particularly at breakfast.

Measure your waist rather than your weight. It tracks the fat that matters here.

Change the shape of your carbohydrate — form, timing, pairing — rather than the quantity of your food.

Walk after meals.

Notice that none of that requires eating less. For you, it probably shouldn't.

Worth asking for

Fasting insulin, or HOMA-IR. In someone at a normal weight with a creeping A1C, these are more informative than glucose alone and rarely ordered without a request.

Try this week: measure your waist and add a second resistance session. Those two address the actual mechanism.

Education, not medical advice.