Exchanging carbohydrate or protein for fat improves lipid-related cardiovascular risk profile in overweight men and women when consumed ad libitum.

BACKGROUND: The impact of low-fat diets on the plasma lipoprotein profile is incompletely understood. METHODS: We conducted two 16-week dietary studies to compare the effects of a moderate-fat (mod-FAT) baseline diet with isocaloric and ad libitum low-fat diets rich in either carbohydrates (high-CHO, n = 16) or protein (high-PRO, n = 19) on plasma lipids, post-heparin lipase activities, cholesteryl ester transfer protein, and phospholipid transfer protein. RESULTS: Switching from the mod-FAT to the isocaloric high-CHO diet lowered plasma high-density lipoprotein cholesterol concentrations (P < 0.001) and tended to increase triglyceride levels (P = 0.087). Cholesterol content in the larger, buoyant low-density lipoprotein (LDL) fractions decreased, whereas those of the very-low-density lipoprotein, intermediate-density lipoprotein, and smaller, denser LDL fractions tended to increase. These changes were largely reversed when subjects lost weight by consuming this high-CHO diet ad libitum. Switching from the mod-FAT diet to the isocaloric high-PRO diet did not increase cholesterol content in the small-dense LDL fraction and led to decreases in both LDL and high-density lipoprotein cholesterol in plasma (P < 0.001 for both).Consumption of the high-protein ad libitum diet accompanied by weight loss did not change plasma lipids further, except for a shift of cholesterol from dense low-density lipoprotein fractions to more buoyant low-density lipoprotein fractions. Cholesteryl ester transfer protein concentrations decreased with high-cholesterol feeding, whereas cholesteryl ester transfer protein concentrations and hepatic lipase and phospholipid transfer protein activities all decreased during high-protein feeding. CONCLUSIONS: Both high-CHO and high-PRO diets improve plasma lipid-related risk of cardiovascular disease when consumed ad libitum.

Initial efficacy of MI, TTM tailoring and HRI's with multiple behaviors for employee health promotion.

OBJECTIVE: This study was designed to compare the initial efficacy of Motivational Interviewing (MI), Online Transtheoretical Model (TTM)-tailored communications and a brief Health Risk Intervention (HRI) on four health risk factors (inactivity, BMI, stress and smoking) in a worksite sample. METHOD: A randomized clinical trial assigned employees to one of three recruitment strategies and one of the three treatments. The treatment protocol included an HRI session for everyone and in addition either a recommended three TTM online sessions or three MI in person or telephone sessions over 6 months. At the initial post-treatment assessment at 6 months, groups were compared on the percentage who had progressed from at risk to taking effective action on each of the four risks. RESULTS: Compared to the HRI only group, the MI and TTM groups had significantly more participants in the Action stage for exercise and effective stress management and significantly fewer risk behaviors at 6 months. MI and TTM group outcomes were not different. CONCLUSION: This was the first study to demonstrate that MI and online TTM could produce significant multiple behavior changes. Future research will examine the long-term impacts of each treatment, their cost effectiveness, effects on productivity and quality of life and process variables mediating outcomes.

Changes in plasma amino Acid levels do not predict satiety and weight loss on diets with modified macronutrient composition.

OBJECTIVE: Serotonin mediates satiety in the central nervous system. Brain serotonin content depends on the plasma ratio of tryptophan (Trp) to large neutral amino acids (LNAA) and may be affected by diet composition. We examined whether high-carbohydrate or high-protein diets induce satiety and weight loss by altering plasma concentrations of these amino acids. METHODS: In study 1 (n = 16, BMI = 27.0 +/- 2.3), we compared plasma Trp and LNAA concentrations averaged over 24 h after 2 weeks of consuming isocaloric diets containing either 45 or 65% of total energy as carbohydrate. In study 2 (n = 19, BMI = 26.2 +/- 2.1), we made the same measurements following diets containing either 15 or 30% of total energy as protein. To assess satiety in both studies, we recorded caloric intake and weight changes during a subsequent 12-week period of ad libitum consumption of the experimental diets. RESULTS: Ad libitum caloric intake fell by 222 +/- 81 kcal/day with a 3.7 +/- 0.6 kg weight loss at 12 weeks in study 1. Ad libitum caloric intake fell by 441 +/- 63 kcal/ day with a 4.9 +/- 0.5 kg weight loss at 12 weeks in study 2. The 24-hour averaged plasma concentration of Trp and the Trp:LNAA ratio were unaffected by the isocaloric increase in carbohydrate or protein consumption that preceded the ad libitum administration of the 2 diets. CONCLUSION: An increase in either carbohydrate or protein intake increases satiety and leads to significant weight loss, however, these effects are not mediated by an increase in plasma concentration of Trp or the Trp:LNAA ratio.

A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations.

BACKGROUND: Ad libitum, low-carbohydrate diets decrease caloric intake and cause weight loss. It is unclear whether these effects are due to the reduced carbohydrate content of such diets or to their associated increase in protein intake. OBJECTIVE: We tested the hypothesis that increasing the protein content while maintaining the carbohydrate content of the diet lowers body weight by decreasing appetite and spontaneous caloric intake. DESIGN: Appetite, caloric intake, body weight, and fat mass were measured in 19 subjects placed sequentially on the following diets: a weight-maintaining diet (15% protein, 35% fat, and 50% carbohydrate) for 2 wk, an isocaloric diet (30% protein, 20% fat, and 50% carbohydrate) for 2 wk, and an ad libitum diet (30% protein, 20% fat, and 50% carbohydrate) for 12 wk. Blood was sampled frequently at the end of each diet phase to measure the area under the plasma concentration versus time curve (AUC) for insulin, leptin, and ghrelin. RESULTS: Satiety was markedly increased with the isocaloric high-protein diet despite an unchanged leptin AUC. Mean (+/-SE) spontaneous energy intake decreased by 441 +/- 63 kcal/d, body weight decreased by 4.9 +/- 0.5 kg, and fat mass decreased by 3.7 +/- 0.4 kg with the ad libitum, high-protein diet, despite a significantly decreased leptin AUC and increased ghrelin AUC. CONCLUSIONS: An increase in dietary protein from 15% to 30% of energy at a constant carbohydrate intake produces a sustained decrease in ad libitum caloric intake that may be mediated by increased central nervous system leptin sensitivity and results in significant weight loss. This anorexic effect of protein may contribute to the weight loss produced by low-carbohydrate diets.