Iris Shai links losing deep belly fat to a healthier brain and lower diabetes risk

A team led by Prof. Iris Shai, an epidemiologist at Ben-Gurion University of the Negev, Reichman University and the Harvard T.H. Chan School of Public Health, reported in spring 2026 that reducing visceral fat, the deep fat packed around the abdominal organs, is linked to slower brain aging in later life. The study, with Dafna Pachter as first author, appeared in Nature Communications and was publicised by Ben-Gurion University on 4 May 2026. A companion paper in the journal Circulation in June tied the same kind of fat loss to lower long-term diabetes risk.

The brain study drew on 533 people in late middle age, mostly men and mostly overweight, who had taken part in one of four long, carefully controlled diet trials run by Shai's group in Israel: DIRECT, CASCADE, CENTRAL and DIRECT-PLUS. The researchers brought them back 5 to 16 years later for repeated MRI scans of the abdomen and brain and for memory and thinking tests. Those who built up the least visceral fat over the years scored higher on cognitive tests and kept more total brain and grey matter volume, along with a healthier hippocampus, the region central to memory. In a subgroup scanned three times over five years, persistently high visceral fat went with faster shrinkage of the hippocampus. The same patterns did not appear for fat under the skin or for body mass index.

Fasting blood sugar and the long-term glucose marker HbA1c were the only blood measures that predicted the pace of brain change, which suggests that insulin resistance may be the link between belly fat and the brain. The Circulation study found that people who regained weight after the trials often did not regain the visceral fat they had lost, and that each 10% drop in visceral fat during a trial was associated with a 28% lower risk of type 2 diabetes a decade later.

The results are associations rather than proof of cause, and the participants were not representative of everyone. Still, Shai described visceral fat and blood sugar as targets in midlife that can be measured and changed.