A 35% drop in diabetes from lifestyle change, with under a kilo of weight loss

People of South Asian origin carry a high risk of type 2 diabetes and a high risk of dying from a cause attributable to it, which makes prevention in this group a pressing question. Lifestyle programmes built on diet and physical activity are a mainstay of diabetes prevention, but the trials run in South Asian populations had suggested more modest effects than those seen in European-origin populations. Each individual study was too small to settle the matter on its own. The researchers therefore set out to pool the raw participant data from every eligible trial worldwide and ask whether lifestyle modification genuinely prevents diabetes in South Asian adults at high risk.

The team searched four major research databases up to 24 September 2018 for randomised trials of diet and physical activity interventions in South Asian adults. Six trials qualified, four conducted in Europe and two in India, and the researchers obtained individual participant data on all 1816 people involved. They pooled the results to estimate the effect on new cases of diabetes, the primary outcome, along with fasting glucose, glucose measured two hours after a sugar load, body weight and waist circumference. They also checked whether the effect differed by sex, body mass, age, study duration or region, and formally graded the certainty of the evidence.

Diabetes developed in 12.6% of participants in the intervention groups against 20.0% in the control groups, a 35% relative reduction and an absolute reduction of 7.4%, with no sign that the benefit differed by sex, body mass, age, study duration or region. The physical changes behind it were modest: two hour glucose fell by 0.34 mmol/l, weight by 0.75 kg and waist circumference by 1.16 cm on average, while fasting glucose did not change at all. Weight loss did differ by region, averaging 1.10 kg in the European trials but only 0.08 kg in the Indian ones. The evidence overall was rated as moderate quality.

This pooled analysis pushes back against the earlier impression that lifestyle modification works less well in South Asian populations than in European-origin ones. It shows a clinically important reduction in diabetes incidence that is consistent across subgroups, and it does so even though the changes in weight and waist were small. That gap between modest adiposity change and substantial risk reduction is itself an open question, since it suggests the benefit does not run purely through weight loss. What remains untested here is how to deliver such programmes at scale, and the authors argue that wide implementation in high-risk South Asian communities in Europe would cut diabetes incidence in those populations.

For readers of South Asian heritage, this is a reason to think that changes to diet and physical activity meaningfully lower the odds of developing type 2 diabetes, even when the bathroom scale barely registers the effort. The consistency of the result across men and women, age groups and regions makes it harder to dismiss as a quirk of one trial or one setting. It is also a useful corrective to the idea that prevention only counts if it produces visible weight loss, since here the protection arrived alongside less than a kilogram of average change. None of this says which specific programme works best; the trials combined diet and activity in different ways.