More evidence debunking the notion that you can be “fat but fit” comes from a study in the European Heart Journal that included thousands of Europeans over a 12-year period.
Those who were overweight or obese but “metabolically healthy”—that is, they had normal blood pressure, blood triglycerides, and blood sugar levels, for instance—were still about 25 percent more likely to develop coronary heart disease than people at healthy body weight.
Accumulation of fat, particularly in the abdomen, has long been linked to elevated heart and other health risks, but earlier studies suggested that any adverse effects were negated in overweight and obese people who were otherwise metabolically healthy.
This latest study, however, "suggests that 'metabolically healthy' obesity is not a benign condition" and that everyone should strive for normal body weight regardless of their metabolic status—though, of course, as the study also found, it’s still far better to be “fat and fit” than “fat and unfit.”
Also see On a Diet? Do This, Not That.