The effect of protease inhibitors derived from potato formulated in a minidrink on appetite, food intake and plasma cholecystokinin levels in humans.

BACKGROUND: Protease inhibitor 2 derived from potato (PI2) is claimed to reduce appetite and food intake, stimulate the satiety hormone cholecystokinin (CCK) and lower postprandial glucose peaks when taken before a meal. However, current literature is inconclusive with regard to its efficacy and mechanism. Furthermore, the potential effect of PI2 on appetite motivational ratings without an immediately following meal has not previously been reported. OBJECTIVE: To comprehensively test the effects of 30 mg PI2 in a minidrink on appetite ratings, subsequent food intake, and plasma CCK and glucose responses. DESIGN: Minidrinks with or without 30 mg PI2 were compared in three separate substudies (A, B and C), each using a two-way, placebo-controlled, balanced-order, cross-over design and 23 or 24 subjects (mean over groups: body mass index 25.0 kg m(-2), range 22.5-30.7 kg m(-2); age 41.3, range 18-62 years). The minidrink was given (A) 120 or (B) 30 min before an ad libitum lunch or (C) 30 min before a fixed lunch. Study parameters were self-reported satiety (substudies A and C), ad libitum meal intake (substudies A and B), and (in an n=12 subset) plasma CCK and blood glucose in all substudies. All results were analyzed using analysis of covariance. Protease-inhibitory activity of the PI2-containing minidrinks was assessed under simulated gut conditions. RESULTS: PI2 did not differ from control for any study parameters, in any substudy, despite confirmation of the inhibitory activity of PI2. CONCLUSIONS: In this study protease inhibition using PI2 in a minidrink at a dose of 30 mg, as commercially used, had no (functional) efficacy on a range of behavioral and physiological appetite and intake control measures.

Metabolically active functional food ingredients for weight control.

The scale of the obesity epidemic creates a pressing consumer need as well as an enormous business opportunity for successful development and marketing of food products with added benefits for weight control. A number of proposed functional food ingredients have been shown to act post-absorptively to influence substrate utilization or thermogenesis. Characteristics and supporting data on conjugated linoleic acid, diglycerides, medium-chain triglycerides, green tea, ephedrine, caffeine, capsaicin and calcium, are reviewed here, giving examples of how these could act to alter energy expenditure or appetite control. Consideration is also given to other factors, in addition to efficacy, which must be satisfied to get such ingredients into foods. We conclude that, for each of the safe, putatively metabolically active agents, there remain gaps in clinical evidence or knowledge of mechanisms, which need to be addressed in order to specify the dietary conditions and food product compositions where these ingredients could be of most benefit for weight control.

Metabolic effects of green tea and of phases of weight loss.

The effect of ingestion of green tea (GT) extract along with a low-energy diet (LED) on health-related blood parameters, and the relationships among changes in metabolic parameters and phases of weight loss were assessed. A double-blind, placebo-controlled, parallel design was used. 46 female subjects (BMI 27.7+/-1.8 kg/m(2)) were fed in energy balance from days 1 to 3, followed by a LED with GT (n=23) or placebo (PLAC, n=23) from days 4 to 87. The LED-period consisted of a phase 1 of 4 weeks (days 4-32) followed by a phase 2 of 8 weeks (days 32-87). Body composition and fasting blood samples were determined on days 4, 32 and 87. No significant differences were observed between the blood parameters of the PLAC and GT group. In phase 1 compared to phase 2 the rate of weight loss was 0.09+/-0.05 kg/day vs. 0.03+/-0.03 kg/day (p<0.001); Fat free mass (FFM) was 21% of weight loss in phase 1 vs. 7% in phase 2 (ns). Surprisingly, favourable changes in free fatty acids, triacylglycerol, beta-hydroxybutyrate, glucose and total cholesterol in phase 1 were reversed in phase 2 (p<0.01). Taken together, GT supplementation during a LED had no effect on health-related blood parameters. Initial improvements in several blood measures at day 32 were reversed by day 87, despite continued weight loss. Modest weight loss improved HDL cholesterol and blood pressure.

The effect of guar gum addition to a semisolid meal on appetite related to blood glucose, in dieting men.

OBJECTIVE: To investigate whether addition of modified guar gum (GG) to a low-energy semisolid meal might be effective on appetite by modifying the response of blood glucose and other blood parameters. DESIGN: Three intervention periods of 2 weeks each, separated by washout periods of 4 weeks. Randomized and cross-over design. SUBJECTS: Fifteen overweight male subjects (mean+/-s.d.; age, 44+/-9 y; body mass index, 28.6+/-1.8 kg/m(2)). INTERVENTION: Subjects consumed a low-energy diet divided over three times a day, consisting of a semisolid meal with (SSM+) or without (SSM) addition of 2.5 g GG, or a solid meal (SM) with the same energy content (947 kJ) and macronutrient composition, plus a dinner of the subject's own choice. At the end of each intervention, time and number of meal initiations, dynamics of blood glucose and other blood parameters, and appetite ratings such as hunger and satiety were determined in a time-blinded situation. RESULTS: The changes in blood glucose from meal initiation to blood glucose peak and from peak to nadir were smaller with SSM+ and SM compared to SSM. Satiety before the third meal was higher with SSM+ and SM compared to SSM (P<0.01). Meal pattern, general appetite and total energy intake were similar for all treatments. CONCLUSIONS: We conclude that, similar to SM, SSM+ resulted in a more moderate change in blood glucose compared to SSM and positively affected satiety before the third meal, while general appetite, total energy intake and meal pattern did not differ.

The effects of 2-week ingestion of (--)-hydroxycitrate and (--)-hydroxycitrate combined with medium-chain triglycerides on satiety, fat oxidation, energy expenditure and body weight.

OBJECTIVE: Assessment of the effect of 2-week supplementation with (--)-hydroxycitrate (HCA) and HCA combined with medium-chain triglycerides (MCT) on satiety, fat oxidation, energy expenditure (EE) and body weight (BW) loss. DESIGN: Three intervention periods of 2 weeks separated by washout periods of 4 weeks. Double-blind, placebo-controlled, randomised and cross-over design. SUBJECTS: Eleven overweight male subjects (mean+/-s.d.; age, 47+/-16 y; body mass index, 27.4 +/- 8.2 kg/m(2)). INTERVENTION: Subjects consumed three self-selected meals and four iso-energetic (420 kJ) snacks daily with either no supplementation (PLA), 500 mg HCA (HCA) or 500 mg HCA and 3 g MCT (HCA+MCT). Each intervention ended with a 36 h stay in the respiration chamber. RESULTS: There was a significant BW loss during the 2 weeks of intervention (PLA, -1.0 +/- 0.4 kg, P<0.05; HCA, -1.5 +/- 0.5 kg, P<0.01; HCA+MCT, -1.3 +/- 0.2 kg, P<0.001), but this reduction was not different between treatments. 24 h EE (PLA, 11.8 +/- 0.2 MJ; HCA, 11.7 +/- 0.1 MJ; HCA+MCT, 11.5 +/- 0.1 MJ), 24 h RQ (0.85 +/- 0.00 in all treatments) and the area under the curve of the appetite-related parameters were not different between treatments. CONCLUSION: Two-week supplementation with HCA and HCA combined with MCT did not result in increased satiety, fat oxidation, 24 h EE or BW loss compared to PLA, in subjects losing BW.

Effects of 2-week ingestion of (-)-hydroxycitrate and (-)-hydroxycitrate combined with medium-chain triglycerides on satiety and food intake.

The aim of this study was to assess the effects of 2 weeks of supplementation with (-)-hydroxycitrate (HCA) and HCA combined with medium-chain triglycerides (MCT) on satiety and energy intake. The experimental design consisted of three intervention periods of 2 weeks separated by washout periods of 2 or 6 weeks in a double-blind, placebo-controlled, randomized, and crossover design. Seven male and 14 female normal to moderately obese subjects (mean+/-S.D.; age, 43+/-10 years; body mass index, 27.6+/-2.0 kg/m(2)) participated in this study. Subjects consumed three self-selected meals and four isoenergetic snacks daily with either no supplementation (PLA), with 500 mg HCA (HCA), or 500 mg HCA and 3 g MCT (HCA+MCT). Each intervention period ended with a test day, consisting of a standardized breakfast and ad libitum a lunch and a dinner. There was a significant body weight (BW) loss during the 2 weeks of intervention (PLA, -0.5+/-0.3 kg, P<.05; HCA, -0.4+/-0.2 kg, P<.05; HCA+MCT, -0.7+/-0.2 kg, P<.01), but this reduction was not different between treatments. Twenty-four-hour energy intake (PLA, 8.1+/-0.3 MJ; HCA, 8.3+/-0.3 MJ; HCA+MCT, 8.4+/-0.3 MJ) and the area under the curve of the appetite-related parameters during the test day were similar for all treatments. Two weeks of supplementation with HCA and HCA combined with MCT did not result in increased satiety or decreased energy intake compared to placebo in subjects losing BW.