The effect of diets high in protein or carbohydrate on inflammatory markers in overweight subjects.

AIM: Increased levels of inflammatory markers have been associated with weight gain and cardiovascular disease. The aim of the present study was to investigate the effect of diets high in either carbohydrate or protein on the inflammatory markers C-reactive protein (CRP), haptoglobin and transferrin in plasma after weight loss. METHODS: Fifty overweight subjects [age: 18-56 years, body mass index (BMI): 27-34] were randomly assigned to an ad libitum, fat-reduced diet (30% of energy, E%), either high in protein and low in carbohydrate (25 E and 45 E% respectively) or high in carbohydrate and low in protein (58 E and 12 E% respectively), during 6 months of strictly controlled dietary intervention with dietary counselling. RESULTS: An average reduction of 25% in CRP and an average increase of 20% in haptoglobin and transferrin were seen in both groups, however, these changes were not significant. In cross-sectional analyses after the intervention CRP was associated with fat mass (r = 0.323, p = 0.03), and the changes in CRP were associated with various indices of body fatness (Deltabody weight r = 0.346, p = 0.02). Changes in body fatness were positively associated with Deltatransferrin (r = 0.344, p = 0.02) and nearly significantly associated with Deltahaptoglobin (r = 0.271, p = 0.07) after 6 months. Multiple regression analysis showed no associations between dietary protein and carbohydrate content and serum CRP, haptoglobin or transferrin concentrations, and this remained unaltered after adjustment for weight change. CONCLUSION: Dietary carbohydrate/protein ratio has no effect on inflammatory markers, but the study confirmed that body fatness is positively associated with levels of serum CRP.

Effect of normal-fat diets, either medium or high in protein, on body weight in overweight subjects: a randomised 1-year trial.

BACKGROUND: We have previously reported that a fat-reduced high-protein diet had more favourable effects on body weight loss over 6 months than a medium-protein diet. OBJECTIVE: To extend this observation by a further 6-12 months less stringent intervention and a 24 months follow-up. DESIGN: A randomised 6 months strictly controlled dietary intervention followed by 6-12 months dietary counselling period, and a subsequent 24 months follow-up, comparing an ad libitum, fat-reduced diet (30% of energy) either high in protein (25% of energy, HP) or medium in protein (12% of energy, MP). SUBJECTS: A total of 50 overweight and obese subjects (age: 19-55 y; BMI: 26-34 kg/m(2)). MEASUREMENTS: Change in body weight, body composition and blood parameters. RESULTS: After 6 months, the HP group (n=23) achieved a greater weight loss than the MP group (n=23) (9.4 vs 5.9 kg) (P<0.01). After 12 months, 8% had dropped out in the HP vs 28% in the MP group (P<0.07). After 12 months, the weight loss was not significantly greater among the subjects in the HP group (6.2 and 4.3 kg), but they had a 10% greater reduction in intra-abdominal adipose tissue and more in the HP group (17%) lost >10 kg than in the MP (P<0.09). At 24 months, both groups tended to maintain their 12 months weight loss, but more than 50% were lost to follow-up. CONCLUSION: A fat-reduced diet high in protein seems to enhance weight loss and provide a better long-term maintenance of reduced intra-abdominal fat stores.

Changes in renal function during weight loss induced by high vs low-protein low-fat diets in overweight subjects.

BACKGROUND: Due to the high satiating effect of protein, a high-protein diet may be desirable in the treatment of obesity. However the long-term effect of different levels of protein intake on renal function is unclear. OBJECTIVE: To assess the renal effects of high vs low protein contents in fat-reduced diets. DESIGN: Randomized 6 months dietary intervention study comparing two controlled ad libitum diets with 30 energy (E%) fat content: high-protein (HP; 25 E%) or low-protein, (LP, 12 E% protein). All food was provided by self-selection in a shop at the department, and high compliance to the diet composition was confirmed by measurements of urinary nitrogen excretion. SUBJECTS: 65 healthy, overweight and obese (25

Randomized trial on protein vs carbohydrate in ad libitum fat reduced diet for the treatment of obesity.

OBJECTIVE: To study the effect on weight loss in obese subjects by replacement of carbohydrate by protein in ad libitum consumed fat-reduced diets. DESIGN: Randomized dietary intervention study over six months comparing two ad libitum fat reduced diets (30% of total energy) strictly controlled in composition: High-carbohydrate (HC, protein 12% of total energy) or high-protein (HP, protein 25% of total energy). SETTING AND PARTICIPANTS: Subjects were 65 healthy, overweight and obese subjects (50 women, 15 men, aged 18-55 y) randomly assigned to HC (n = 25), HP (n = 25) or a control group (C, n = 15). All food was provided by self-selection in a shop at the department, and compliance to the diet composition was evaluated by urinary nitrogen excretion. MAIN OUTCOME MEASURE: Change in body weight, body composition and blood lipids. RESULTS: More than 90% completed the trial. Weight loss after six months was 5.1 kg in the HC group and 8.9 kg in the HP group (difference 3.7 kg, 95% confidence interval (CI)(1.3-6.2 kg) P < 0.001), and fat loss was 4.3 kg and 7.6 kg, respectively (difference 3.3 kg (1.1-5.5 kg) P < 0.0001), whereas no changes occurred in the control group. More subjects lost > 10 kg in the HP group (35%) than in the HC group (9%). The HP diet only decreased fasting plasma triglycerides and free fatty acids significantly. CONCLUSIONS: Replacement of some dietary carbohydrate by protein in an ad libitum fat-reduced diet, improves weight loss and increases the proportion of subjects achieving a clinically relevant weight loss. More freedom to choose between protein-rich and complex carbohydrate-rich foods may allow obese subjects to choose more lean meat and dairy products, and hence improve adherence to low-fat diets in weight reduction programs.

A method to achieve control of dietary macronutrient composition in ad libitum diets consumed by free-living subjects.

OBJECTIVE: To validate a shop system in controlling macronutrient composition during ad libitum dietary intervention. DESIGN: Six months randomized intervention trial. SETTING: A shop at the department from which all foods were collected free of charge and registered by a purpose-designed computer system. SUBJECTS: Sixty-five free-living obese subjects (25 kg/m2 < BMI < 34 kg/m2) recruited through advertisement and from a waiting list at the Department. Total drop-out rate was 8%. INTERVENTIONS: Ad libitum low-fat diets (30 energy-% (E%) fat): (1) High-protein (25 E% protein, HP) or (2) Low-protein, (12 E% protein, LP) or habitual diet (controls, C). MAIN OUTCOME MEASURES: Compliance was assessed by 24 h urinary nitrogen excretion (24 h UN). RESULTS: After one month of dietary intervention 24 h UN increased significantly in the HP group and decreased significantly in the LP group (Group difference 95% CI):6.8 g (5.0-8.7 g), P < 0.0001). This group difference remained throughout the trial. There was good agreement between protein intake as estimated by the shop computer and as estimated from 24 h UN in both first (r = 0.86) and second half of the intervention (r = 0.80). CONCLUSION: The high dietary compliance demonstrates the potential of this method to control macronutrient composition in ad libitum dietary intervention studies in free-living subjects.

The role of low-fat diets and fat substitutes in body weight management: what have we learned from clinical studies?

The introduction of low-fat, high-complex carbohydrate diets far the prevention and treatment of obesity was based on the causal link established between dietary fat and body fatness. Observational and mechanistic studies show that because fat possesses a lower satiating power than carbohydrate and protein, a diet rich in fat can increase energy intake. The propensity to gain weight is enhanced in susceptible persons, particularly sedentary people who have a genetic predisposition to obesity. Low-fat diets cause weight loss proportional to pretreatment body weight in a dose dependent manner; that is, weight loss is correlated positively to the reduction in dietary fat content. A reduction of 10% fat energy produces an average 5-kg weight loss in obese persons. As with traditional caloric counting diets, obese persons lose weight only if they adhere to the prescribed low-fat diet. Failure to achieve a weight loss and to maintain it may be attributed in part to lack of adherence to the diet. After a major weight loss, an ad libitum low-fat diet program appears to be superior to caloric counting in maintaining the weight loss 2 years later. Replacing some fat with protein instead of carbohydrate may increase the weight loss further. Moreover, fat substitutes may make it easier to prevent and treat obesity by making the diet palatable. More randomized, controlled, long-term dietary intervention studies are warranted to identify the optimal diet composition for the treatment of obesity.

Normal levels of energy expenditure in patients with reported "low metabolism'.

The present study examined the hypothesis that patients with apparent diet-resistant obesity have subnormal energy expenditure. Ten biochemically euthyroid patients (eight women and two men), aged 21-76 years, with either excessive gynoid fat distribution or obesity (BMI 23.8-41.0), were referred to the department thought to be suffering from a low metabolic rate syndrome since dietary records showed very low energy intake (< 5 MJ day-1) in combination with failure to lose weight on low-energy diets. Twenty-four-hour energy expenditure (24-h EE), basal energy expenditure (BEE) and sleeping energy expenditure (SEE) were measured in a respiration chamber on a fixed activity programme. The patients consumed a diet containing 37 energy-per cent (E%) fat, 47 E% carbohydrate and 16 E% protein. The individual energy intake was estimated from a previously established algorithm between 24-h EE and fat-free mass (FFM) estimated by bioimpedance. Results were compared with equivalent values in a reference population of 76 subjects ranging from normal weight to obese. No evidence of low metabolism was found in terms of adjusted 24-h EE in the patients with diet resistance when compared with the control group (9263 +/- 819 kJ vs. 9211 +/- 558 kJ). No differences were found when comparing adjusted BEE and SEE in the two groups (7655 +/- 727 vs. 7411 +/- 770 kJ 24 h-1 and 7048 +/- 672 vs. 6911 +/- 408 kJ 24 h-1). The physical activity index (PAI) during the chamber stay was likewise within normal values (1.32 +/- 0.07 vs. 1.34 +/- 0.04; NS).