After 30 years of policy based on the Diet Heart (low-fat) Hypothesis, obesity and type 2 diabetes are now an epidemic. Recently published research seriously questions the dangers of dietary saturated fats and also any potential health benefits of a low-fat diet for the general population. In the context of these seismic changes in evidence-based nutrition, it is time to revisit our perspective of carbohydrate-restricted diets, not only for weight loss but also for the long-term management of conditions associated with insulin resistance. In randomized trials comparing high-carbohydrate versus low-carbohydrate diets, a well-formulated low-carbohydrate diet reduced the absolute concentration of saturated fat in serum lipids. This apparent paradox is explained by the accelerated β-oxidation of saturated fatty acids when humans are adapted to a ketogenic diet. Given that this keto-adapted state is also associated with no reduction in physical performance and reduced inflammation, carbohydrate-restricted diets may play an important role in the prevention and treatment of diseases of insulin resistance such as metabolic syndrome and type 2 diabetes.