Evolution of the diabetic diet: Fats and fallacies

Abstract

The Diabetes Control and Complications Trial and United Kingdom Prospective Diabetes Study (UKPDS) trials have provided evidence for the pivotal importance of optimizing glycaemic control to prevent complications in type 1 and 2 diabetes mellitus. Both patients and diabetes professionals consider lifestyle change and appropriate medication as cornerstones for achieving good glycaemic control. The frequent reversals in the recommended diabetic diet in the past century warn that in the nutritional area the hypotheses are many, but the proofs are few. In type 1 diabetes, the patient is still advised to spread out carbohyrate foods during the day with three short-acting insulin injections at meal times to minimize postprandial hyperglycaemia. In type 2 diabetes, weight loss is the major target, because 80% of patients are overweight or obese. However, it is salutory to note that in the UKPDS trial, no modality of treatment delayed the relentless deterioration of glycaemic control in type 2 diabetes, the extent of which was predicted by the insulin secretion. Controversy still exists regarding whether lowering the dietary fat enhances weight loss of itself and whether dietary carbohydrate, fat and fibre influence insulin sensitivity and glycaemia. The American Diabetes Association's evidence-based recommendations currently offer a choice between a high carbohyrate and modified fat diet, with monounsaturated fat replacing the saturated fat instead of carbohydrate. The role of omega-3 fatty acids in man is not resolved. The reason for the surprising lack of definitive evidence lies in the limitations of nutritional research. Under-reporting of diet is common and dietary assessment tools are often inaccurate. Sustained weight loss is unattainable by the majority of patients, perhaps because of the strongly genetic nature of obesity and the sedentary lifestyle. Compliance may be improved by suggesting small, sustained dietary changes, setting small weight loss targets and encouraging a permanent increase in total activity.