• Although diet therapy is considered the cornerstone of therapy for obese patients with non–insulin-dependent diabetes mellitus, losing weight is often difficult, and the plasma glucose concentration does not always improve after weight loss. We looked for predictors of improvement in plasma glucose levels after weight loss in 135 obese patients with non-insulin-dependent diabetes mellitus who had lost at least 9.1 kg of body weight. After weight loss there was a bimodal distribution of plasma glucose levels, allowing us to identify patients as "responders" or "nonresponders" according to whether a random plasma glucose level was above or below 10.0 mmol/L after a 9.1-kg weight loss. Fifty-five (41%) of 135 patients were responders (after a 9.1-kg weight loss, the mean ± SEM plasma glucose level was 7.0±0.2 mmol/L). Many responders had improved plasma glucose levels after only slight weight loss. Eighty (59%) of 135 patients were nonresponders (after a 9.1-kg weight loss, the mean±SEM plasma glucose level was 18.3±0.6 mmol/L). Although the responder and nonresponder groups were comparable in age, sex distribution, plasma glucose levels, and body weight at initial presentation, improvement in the plasma glucose level after weight loss could be predicted by a plasma glucose level of 10.0 mmol/L or lower after 2.3-kg (62% positive predictive value) and 4.5-kg (79% positive predictive value) weight loss. We conclude that, in contrast to conventional teaching, many patients with non–insulin-dependent diabetes mellitus will not have any improvement in plasma glucose levels after a 9.1-kg weight loss. However, a substantial minority (≈40%) of obese patients with non–insulin-dependent diabetes mellitus have much lower plasma glucose levels with a weight loss of 9.1 kg or less. Although the plasma glucose response to weight loss cannot be forecast by initial clinical parameters, the success or failure of diet therapy can be predicted from the plasma glucose level after a weight loss of only 2.3 to 4.5 kg. Mild or moderately obese patients with non–insulin-dependent diabetes mellitus who remain hyperglycemic after a weight loss of 2.3 to 9.1 kg are unlikely to improve with further weight loss and should be considered for treatment with insulin or oral hypoglycemic agents.
(Arch Intern Med. 1990;150:803-806)