Authoritative medical evidence supports this claim. Major health bodies state that type 2 diabetes can often be prevented or delayed, particularly in people at higher risk, through lifestyle changes such as healthier eating, regular physical activity, and weight loss. The claim does not imply every case is preventable, and that limitation is consistent with the evidence.
Caveats
"Often preventable" does not mean universally preventable; some people develop type 2 diabetes despite healthy behavior because of genetics, age, or other factors.
Most prevention evidence is strongest for people with prediabetes or other elevated risk factors, so results are not identical for every population.
Real-world prevention depends on access to healthy food, safe exercise opportunities, medical care, and sustained support.