Circulating lipids in men with type 2 diabetes following 3 days on a carbohydrate-free diet versus 3 days of fasting.

Objective: We have been interested in determining the effects of dietary changes on fuel metabolism and regulation in men with type 2 diabetes mellitus (T2DM). In this study, the changes in 24-hr circulating lipid profiles were determined when the major fuel source was endogenous versus exogenous fat.

Methods: Seven males with T2DM were randomized in a crossover design with a 4-week washout period. A standard mixed (control) diet (30%fat:15%protein:55%carbohydrate) was provided initially. Subsequently, a 72-hr (3-day) fast, or a high fat (85%), 15% protein, essentially carbohydrate-free (CHO-free) diet was provided for 72 hr. Triacylglycerol (TAG), non-esterified fatty acids (NEFA), β-hydroxybutyrate (bHB), and insulin-like growth factor-binding protein-1 (IGFBP-1) profiles were determined during the last 24 hr of intervention, as well as during the control diet.

Results: Regardless of the amount of dietary fat (30% vs 85%) and differences in 24-hr profiles, TAG, NEFA, and bHB all returned to the previous basal concentrations within 24 hr. TAGs and NEFAs changed only modestly with fasting; bHB was elevated and increasing. The IGFBP-1 profile was essentially unchanged with either diet but increased with fasting.

Conclusion: A CHO-free diet resulted in a large increase in TAG and NEFA versus the control diet; however, both were cleared by the following morning. A negative NEFA profile occurred with the control diet. Thus, mechanisms are present to restore lipid concentrations to their original AM concentrations daily. Fasting resulted in stable concentrations, except for a continuing increase in bHB. Glucose and insulin, common fuel regulators, could not explain the results.