A normal BMI does not mean normal metabolic risk. South Asian adults in the MASALA and MESA studies had a type 2 diabetes prevalence of 23% at ages 44 to 84, compared with 6% in white adults [6]. That gap shows up across all BMI ranges, including at weights that screening tools classify as normal. The reason is not settled. Flowers and colleagues added body composition measures to those same studies and did not find strong evidence that fat distribution alone explains the difference [3]. What matters is that a normal BMI is not a reason to skip screening if you have risk factors. This guide explains what the numbers actually say, and what to do next.

Why does diabetes show up at lower weights in this population?

The published research documents that South Asian adults develop type 2 diabetes at lower BMI values than other groups, but the mechanism is not fully explained. In Ontario, Canada, Chiu and colleagues followed 59,824 adults without diabetes and found a hazard ratio of 3.40 for developing diabetes among South Asian adults compared with white adults. In that same cohort, a BMI of 24 in South Asian adults carried the same diabetes incidence rate as a BMI of 30 in white adults. This is Canadian data, not US data, but it illustrates the pattern: the threshold is lower.

One popular explanation points to visceral fat, the fat stored around organs inside the abdomen. The logic is intuitive: if South Asian bodies store fat differently, that might explain the higher risk at lower weights. Flowers and colleagues tested this directly by adding body composition measures to the MASALA and MESA analyses and concluded they did not identify strong evidence that accounting for body composition explains differences in the risk for type 2 diabetes [3]. That does not mean body composition plays no role. It means the published evidence does not show it is the main story.

What remains is that the risk is real and measured, but the reason is not settled. That uncertainty does not change what you should do: a normal BMI is not a screening pass if you have risk factors.

What does a normal BMI actually tell you?

BMI is a population screening tool, not a measurement of any one body. It sorts groups efficiently at scale. It does not measure fat, muscle, bone density, or how your metabolism works. Two people at the same BMI can have very different body compositions and very different metabolic health.

For South Asian adults, the American Diabetes Association recommends screening at a BMI of 23 or higher if you have one or more additional risk factors [1]. That threshold is lower than the standard 25 for other populations, reflecting the research showing that risk appears earlier in this group. A BMI below 23 with no risk factors is lower-risk, but it is not zero-risk, and it is not a reason to skip screening if you have a family history of diabetes, cardiovascular disease, or other factors on the risk list.

The WHO expert consultation on Asian populations identified potential public health action points at BMI values of 23.0, 27.5, 32.5 and 37.5, and noted that the proportion of Asian people at high risk of type 2 diabetes and cardiovascular disease is substantial at BMI values lower than the existing WHO cut-off point for overweight of 25 or higher. That means someone at a BMI of 24 or 25 is not in a safe zone just because they are below the traditional overweight threshold.

What are the risk factors that matter at a normal weight?

The American Diabetes Association lists these risk factors alongside the BMI threshold: a first-degree relative with diabetes, high-risk race, ethnicity and ancestry (the examples given are African American, Latino, Native American and Asian American), a history of cardiovascular disease, hypertension, abnormal cholesterol or triglyceride levels, polycystic ovary syndrome, and physical inactivity [1]. If you have any of these, screening makes sense even at a normal BMI.

Prediabetes usually has no symptoms [2]. Most people who have it do not know. That is why the number matters more than how you feel. Someone at a normal weight with a family history of diabetes or a history of gestational diabetes can have prediabetes and feel completely fine. The only way to know is to test.

What does prediabetes mean, and what happens next?

Prediabetes is the stage between normal blood glucose and type 2 diabetes. An A1C of 5.7% to 6.4% is prediabetes [4]. An A1C of 6.5% or higher is diabetes [4]. Below 5.7% is normal [4].

People with prediabetes have a high chance of developing type 2 diabetes within 5 to 10 years [2]. That is not a certainty. It is a statistical risk. Some people with prediabetes never develop diabetes. But the risk is real enough that screening and early action matter.

Insulin resistance usually accompanies prediabetes. Insulin resistance is a condition in which your body does not respond to insulin the way it should [2]. People with insulin resistance and prediabetes usually have no symptoms [2]. You cannot feel it happening.

What can you actually do if you have prediabetes at a normal weight?

The Diabetes Prevention Program, a major clinical trial, found that losing 5% to 7% of body weight lowered the chance of developing type 2 diabetes [2]. That is a concrete target: modest weight loss can make a measurable difference. The weight loss does not have to be dramatic to matter.

No medication is FDA-approved specifically for the prevention of type 2 diabetes [5]. That does not mean medicines do not exist for this purpose. It means the decision to use any medicine belongs to a clinician who knows your full history, your test results, and your goals.

A structured lifestyle intervention combines education about diet and physical activity with regular check-ins. The SAHELI randomized clinical trial tested a culturally adapted lifestyle intervention with 549 South Asian adults in the Chicago metropolitan area. The trial found it was not more effective than written health education materials for cardiovascular risk factor reduction, though participation was associated with greater improvements in dietary quality, physical activity and self-efficacy [7]. Sehat publishes free cited guides on prediabetes at a normal weight and the Asian BMI 23 screening threshold to help you understand what to ask your clinician about.

Here is what you can act on right now:

  • You have a family history of diabetes, cardiovascular disease, or gestational diabetes
  • You have hypertension, abnormal cholesterol or triglyceride levels, or polycystic ovary syndrome
  • You are physically inactive most days
  • You are of South Asian, African American, Latino, Native American, or Pacific Islander descent
  • Your BMI is 23 or higher

If any of these apply to you, screening makes sense regardless of how you feel or how normal your weight seems.

What to do next

  1. Write down your BMI and your risk factors before your next appointment with your clinician. Bring the list.
  2. Ask your clinician whether an A1C test or fasting glucose test makes sense for you. These are the standard screening tests [1].
  3. If you have not had your blood pressure, cholesterol, and triglycerides checked recently, ask about those too. They are part of the risk picture [1].
  4. If your test results show prediabetes, ask your clinician about a structured lifestyle program and what options are available to you.
  5. If you have a first-degree relative with diabetes, ask them about their diagnosis age and what their clinician recommended. That history matters for your own screening.
  6. Check the guides hub for more on screening, prediabetes, and what the numbers mean.

Sources

  1. American Diabetes Association, Diagnosis and Classification of Diabetes, Standards of Care in Diabetes 2026, screening thresholds and risk factors, accessed 2026-08-06, https://diabetesjournals.org/care/article/49/Supplement_1/S27/163926/2-Diagnosis-and-Classification-of-Diabetes
  2. NIDDK, insulin resistance and prediabetes, symptoms, risk factors, and the Diabetes Prevention Program, accessed 2026-08-06, https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
  3. Flowers and colleagues, body composition and diabetes risk in South Asians, PubMed, accessed 2026-08-06, https://pubmed.ncbi.nlm.nih.gov/30796111/
  4. NIDDK, the A1C test, test ranges and interpretation, accessed 2026-08-06, https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test
  5. American Diabetes Association, Prevention or Delay of Diabetes, Standards of Care in Diabetes, FDA approval status, accessed 2026-08-06, https://pmc.ncbi.nlm.nih.gov/articles/PMC12690170/
  6. Kanaya and colleagues, MASALA and MESA diabetes prevalence, PubMed, accessed 2026-08-06, https://pubmed.ncbi.nlm.nih.gov/24705613/
  7. SAHELI randomized clinical trial, PubMed, accessed 2026-08-06, https://pubmed.ncbi.nlm.nih.gov/39259546/