Effect of a low-glycaemic index-low-fat-high protein diet on the atherogenic metabolic risk profile of abdominally obese men

It has been suggested that the current dietary recommendations (low-fat-hig h-carbohydrate diet) may promote the intake of sugar and highly refined sta rches which could have adverse effects on the metabolic risk profile. We ha ve investigated the short-term (6-d) nutritional and metabolic effects of a n ad libitum low-glycaemic index-low-fat-high-protein diet (prepared accord ing to the Montignac method) compared with the American Heart Association ( AHA) phase I diet consumed ad libitum as well as with a pair-fed session co nsisting of the same daily energy intake as the former but with the same ma cronutrient composition as the AHA phase I diet. Twelve overweight men (BMI 33.0 (sd 3.5) kg/m(2)) without other diseases were involved in three exper imental conditions with a minimal washout period of 2 weeks separating each intervention. By protocol design, the first two conditions were administer ed randomly whereas the pair-fed session had to be administered last. Durin g the ad libitum version of the AHA diet, subjects consumed 11695.0 (sd 116 3.0) kJ/d and this diet induced a 28 % increase in plasma triacylglycerol l evels (1.77 (sd 0.79) v. 2.27 (sd 0.92) mmol/l, P <0.05) and a 10 % reducti on in plasma HDL-cholesterol concentrations (0.92 (sd 0.16) v. 0.83 (sd 0.0 9) mmol/l, P <0.01) which contributed to a significant increase in choleste rol:HDL-cholesterol ratio (P <0.05), this lipid index being commonly used t o assess the risk of coronary heart disease. In contrast, the low-glycaemic index-low-fat-high-protein diet consumed ad libitum resulted in a spontane ous 25 % decrease (P <0.001) in total energy intake which averaged 8815.0 ( sd 738.0) kJ/d. As opposed to the AHA diet, the low-glycaemic index-low-fat -high-protein diet produced a substantial decrease (-35 %) in plasma triacy lglycerol levels (2.00 (sd 0.83) v. 1.31 (sd 0.38) mmol/l, P <0.0005), a si gnificant increase (+1.6 %) in LDL peak particle diameter (251 (sd 5) v. 25 5 (sd 5) Angstrom, P <0.02) and marked decreases in plasma insulin levels m easured either in the fasting state, over daytime and following a 75 g oral glucose load. During the pair-fed session, in which subjects were exposed to a diet with the same macronutrient composition as the AHA diet but restr icted to the same energy intake as during the low-glycaemic index-low-fat-h igh-protein diet, there was a trend for a decrease in plasma HDL-cholestero l levels which contributed to the significant increase in cholesterol:HDL-c holesterol ratio noted with this condition. Furthermore, a marked increase in hunger (P <0.0002) and a significant decrease in satiety (P <0.007) were also noted with this energy-restricted diet. Finally, favourable changes i n the metabolic risk profile noted with the ad libitum consumption of the l ow-glycaemic index-low-fat-high-protein diet (decreases in triacyglycerols, lack of increase in cholesterol:HDL-cholesterol ratio, increase in LDL par ticle size) were significantly different from the response of these variabl es to the AHA phase I diet. Thus, a low-glycaemic index-low-fat-high-protei n content diet may have unique beneficial effects compared with the convent ional AHA diet for the treatment of the atherogenic metabolic risk profile of abdominally obese patients. However, the present study was a short-term intervention and additional trials are clearly needed to document the long- term efficacy of this dietary approach with regard to compliance and effect s on the metabolic risk profile.