Éric Doucet

Appetite after weight loss by energy restriction and a low-fat diet–exercise follow-up

OBJECTIVE: The aim of the present study was to determine the impact of weight loss on appetite as measured by visual analog scale (VAS).METHODS: Seventeen subjects (10 men and seven women) took part in a 15 week weight loss program which consisted of drug therapy (fenfluramine 60 mg/day) or placebo coupled to an energy restriction (−2930 kJ/day; phase 1) followed by an 18 week low-fat diet–exercise follow-up (phase 2). Subjects were given a standardized breakfast before and after phase 1 as well as after phase 2. Individuals were asked to fill out VAS before and at 0, 10, 20, 30, 40, 50 and 60 min after this test meal. Blood samples were drawn before the meal and at 0, 30 and 60 min postprandially and analyzed for glucose and insulin. Fasting plasma cortisol and leptin were also determined.RESULTS: An increase in the fasting desire to eat, hunger and prospective food consumption (PFC) was observed after phase 1 and to an even greater extent after phase 2 in both men and women. In the fasting state, positive correlations were observed between changes in the desire to eat (r=0.76; P<0.05) as well as changes of PFC (r=0.82; P<0.05) and changes in cortisol at the end of phase 1 for women. In response to phase 1, statistically significant correlations were found between changes of hunger (r=0.64; P<0.05) and desire to eat (r=0.67; P<0.05) as measured by AUC in response to the meal and changes of fasting plasma cortisol in men. The most consistent predictor of changes of baseline desire to eat (r=0.68 P<0.05), fullness (r=−0.78, P<0.05) and PFC (r=0.91, P<0.01) during phase 2 was the change in fasting cortisol in men. Changes of fullness were also associated with changes of fasting leptin in men (r=0.68; P<0.05) during phase 2.CONCLUSION: These results suggest that weight loss is accompanied by an increase of baseline appetite in both men and women and that the most consistent predictor of these changes in appetite seems to be changes in fasting plasma cortisol.

Effects of red pepper on appetite and energy intake

Two studies were conducted to investigate the effects of red pepper (capsaicin) on feeding behaviour and energy intake. In the first study, the effects of dietary red pepper added to high-fat (HF) and high-carbohydrate (HC) meals on subsequent energy and macronutrient intakes were examined in thirteen Japanese female subjects. After the ingestion of a standardized dinner on the previous evening, the subjects ate an experimental breakfast (1883 kJ) of one of the following four types: (1) HF; (2) HF and red pepper (10 g); (3) HC; (4) HC and red pepper. Ad libitum energy and macronutrient intakes were measured at lunch-time. The HC breakfast significantly reduced the desire to eat and hunger after breakfast. The addition of red pepper to the HC breakfast also significantly decreased the desire to eat and hunger before lunch. Differences in diet composition at breakfast time did not affect energy and macronutrient intakes at lunch-time. However, the addition of red pepper to the breakfast significantly decreased protein and fat intakes at lunch-time. In Study 2, the effects of a red-pepper appetizer on subsequent energy and macronutrient intakes were examined in ten Caucasian male subjects. After ingesting a standardized breakfast, the subjects took an experimental appetizer (644 kJ) at lunch-time of one of the following two types: (1) mixed diet and appetizer; (2) mixed diet and red-pepper (6 g) appetizer. The addition of red pepper to the appetizer significantly reduced the cumulative ad libitum energy and carbohydrate intakes during the rest of the lunch and in the snack served several hours later. Moreover, the power spectral analysis of heart rate revealed that this effect of red pepper was associated with an increase in the ratio sympathetic: parasympathetic nervous system activity. These results indicate that the ingestion of red pepper decreases appetite and subsequent protein and fat intakes in Japanese females and energy intake in Caucasian males. Moreover, this effect might be related to an increase in sympathetic nervous system activity in Caucasian males.

Appetite sensations and satiety quotient: predictors of energy intake and weight loss.

PURPOSE The aim of this study was to further evaluate the validity and clinical meaningfulness of appetite sensations to predict overall energy intake as well as body weight loss. METHODS Men (n = 176) and women (n = 139) involved in six weight loss studies were selected to participate in this study. Visual analogue scales were used to measure appetite sensations before and after a fixed test meal. Fasting appetite sensations, 1 h post-prandial area under the curve (AUC) and the satiety quotient (SQ) were used as predictors of energy intake and body weight loss. Two separate measures of energy intake were used: a buffet style ad libitum test lunch and a three-day self-report dietary record. RESULTS One-hour post-prandial AUC for all appetite sensations represented the strongest predictors of ad libitum test lunch energy intake (p < or = 0.001). These associations were more consistent and pronounced for women than men. Only SQ for fullness was associated with ad libitum test lunch energy intake in women. Similar but weaker relationships were found between appetite sensations and the 3-day self-reported energy intake. Weight loss was associated with changes in appetite sensations (p < or = 0.01) and the best predictors of body weight loss were fasting desire to eat; hunger; and PFC (p < or = 0.01). CONCLUSIONS These results demonstrate that appetite sensations are relatively useful predictors of spontaneous energy intake, free-living total energy intake and body weight loss. They also confirm that SQ for fullness predicts energy intake, at least in women.

Clinical significance of adaptive thermogenesis

The epidemic of obesity is developing faster than the scientific understanding of an efficient way to overcome it, as reflected by the low success rate of short- and long-term weight loss interventions. From a clinical standpoint, this suggests that the body tends to defend a set point of possible genetic origin in the context of a weight-reducing program. As described in this paper, this limited therapeutic success may depend on adaptive thermogenesis, which represents in this case the decrease in energy expenditure (EE) beyond what could be predicted from the changes in fat mass or fat-free mass under conditions of standardized physical activity in response to a decrease in energy intake. This issue has been documented in recent studies that have shown in obese individuals adhering to a weight reduction program a greater than predicted decrease in EE, which in some cases was quantitatively sufficient to overcome the prescribed energy restriction, suggesting a role for adaptive thermogenesis in unsuccessful weight loss interventions and reduced body weight maintenance. As also discussed in this paper, this ‘adaptive thermogenesis’ can be influenced by environmental factors, which have not been frequently considered up to now. This is potentially the case for plasma organochlorine concentration and oxygen desaturation in obstructive sleep apnea syndrome. It is concluded that health professionals should be aware that in some vulnerable individuals, adaptive thermogenesis can be multi-causal, and has the capacity to compensate, at least partly, for the prescribed energy deficit, possibly going beyond any good compliance of some patients.

Evidence for the existence of adaptive thermogenesis during weight loss

The present study was performed to further investigate the adaptive component of thermogenesis that appears during prolonged energy restriction. Fifteen obese men and twenty obese women underwent a 15-week weight-loss programme. During this programme, body weight and composition as well as resting energy expenditure (REE) were measured at baseline, after 2 and 8 weeks of energy restriction (-2929 kJ/d) and drug therapy (or placebo), and finally 2-4 weeks after the end of the 15-week drug therapy and energy restriction intervention, when subjects were weight stable. Regression equations were established in a control population of the same age. These equations were then used to predict REE in obese men and women at baseline, after 2 and 8 weeks, as well as after the completion of the programme. In both men and women body weight and fat mass were significantly reduced in all cases) while fat-free mass remained unchanged throughout the programme. At baseline, REE predicted from the regression equation was not significantly different from the measured REE in men, while in women the measured REE was 13 % greater than predicted. After 2 weeks of energy restriction, measured REE had fallen by 469 and 635 kJ/d more than predicted and this difference reached 963 and 614 kJ/d by week 8 of treatment in men and women respectively. Once body-weight stability was recovered at the end of the programme, changes in REE remained below predicted changes in men (-622 kJ/d). However, in women changes in predicted and measured REE were no longer different at this time, even if the women were maintaining a reduced body weight. In summary, the present results confirm the existence of adaptive thermogenesis and give objective measurements of this component during weight loss in obese men and women, while they also emphasize that in women this component seems to be essentially explained by the energy restriction.

Combined effects of red pepper and caffeine consumption on 24 h energy balance in subjects given free access to foods

The effects of red pepper and caffeine ingestion on energy and macronutrient balances were examined in eight Caucasian male subjects. All subjects participated in two randomly assigned conditions: control and experimental (red pepper and caffeine). After ingesting a standardized breakfast, subjects ate three meals ad libitum (lunch, dinner and breakfast) and snacks which were served approximately 2 h after the lunch and dinner over a 24 h period. Two appetizers with or without 3 g red pepper) were given before lunch and dinner, and a drink (decaffeinated coffee with or without 200 mg caffeine) was served at all meals and snacks except for the after-dinner snack. It is also important to note that on the experimental day, 8.6 and 7.2 g red pepper were also added to lunch and dinner respectively. Red pepper and caffeine consumption significantly reduced the cumulative ad libitum energy intake and increased energy expenditure. The mean difference in energy balance between both conditions was 4000 kJ/d. Moreover, the power spectral analysis of heart rate suggested that this effect of red pepper was associated with an increase in sympathetic:parasympathetic nervous system activity ratio. These results indicate that the consumption of red pepper and caffeine can induce a considerable change in energy balance when individuals are given free access to foods.

Impact of high-intensity exercise on energy expenditure, lipid oxidation and body fatness

OBJECTIVE: Two studies were conducted to assess the potential of an increase in exercise intensity to alter energy and lipid metabolism and body fatness under conditions mimicking real life.METHODS: Study 1 was based on the comparison of adiposity markers obtained in 352 male healthy adults who participated in the Québec Family Study who either regularly participated in high-intensity physical activities or did not. Study 2 was designed to determine the effects of high-intensity exercise on post-exercise post-prandial energy and lipid metabolism as well as the contribution of β-adrenergic stimulation to such differences under a real-life setting.RESULTS: Results from Study 1 showed that men who regularly take part in intense physical activities display lower fat percentage and subcutaneous adiposity than men who never perform such activities, and this was true even if the latter group reported a lower energy intake (917 kJ/day, P<0.05). In Study 2, the high-intensity exercise stimulus produced a greater post-exercise post-prandial oxygen consumption as well as fat oxidation than the resting session, an effect which disappeared with the addition of propranolol. In addition, the increase in post-prandial oxygen consumption observed after the high-intensity exercise session was also significantly greater than that promoted by the low-intensity exercise session.CONCLUSION: These results suggest that high-intensity exercise favors a lesser body fat deposition which might be related to an increase in post-exercise energy metabolism that is mediated by β-adrenergic stimulation.

Resistance Training Does Not Contribute to Improving the Metabolic Profile after a 6-Month Weight Loss Program in Overweight and Obese Postmenopausal Women

CONTEXT Limited data are available regarding the impact of caloric restriction (CR) in combination with resistance training (RT) on the metabolic profile of postmenopausal women. OBJECTIVE The objective of the study was to determine whether RT adds to CR in improving body composition and the metabolic profile. DESIGN AND SETTING This was a 6-month, randomized, clinical trial. PATIENTS Patients included 107 postmenopausal women (body mass index >27 kg/m(2)). INTERVENTION The intervention was a 6-month CR alone or in combination with a RT program. MAIN OUTCOME MEASURES Fat mass (FM), lean body mass (LBM), abdominal sc fat and visceral fat, fasting lipids, insulin sensitivity, resting blood pressure, and inflammation markers were measured. RESULTS Both groups were similar at baseline and significantly decreased body weight, body mass index, FM, percent FM, abdominal sc fat, and visceral fat after the study (P < 0.001), with greater losses of percent FM and trunk FM in the CR + RT group (P < 0.05). LMB significantly decreased in the CR (-0.9 +/- 2.4 kg) and the CR+RT (-0.4 +/- 2.2 kg) groups (P < 0.005), with no difference between them. Both groups significantly improved plasma triglycerides, fasting insulin level, glucose disposal, and markers of the inflammation profile after weight loss (P < 0.05), with no difference between groups. No improvements were observed for the other variables of interest in both groups. CONCLUSIONS CR+RT was associated with greater losses in percent FM and trunk FM compared with CR alone. However, CR+RT was not associated with additional improvements in the metabolic profile compared with CR alone.

Dietary fat composition and human adiposity

Objectives: This study was undertaken to investigate the relation between dietary fat composition and adiposity in adult men.Subjects: A sample of 128 male subjects who participated in Phase 2 of the Québec Family Study.Design: The association between adiposity and total dietary fat intake (TFI), saturated fat intake (SFA), monounsaturated fat intake (MUFA) and polyunsaturated fat intake (PUFA) was analyzed in the overall sample. A comparison of body fatness was also performed between consumers of high (4th quartile) and low amounts (1st quartile) of TFI, SFA, MUFA and PUFA.Results: Significant positive correlations were found between the percentage of dietary energy as total fat and body fatness. Men in the upper quartile of TFI displayed significantly more adiposity than those in the lower quartile. Significant differences were also observed when quartiles were established using SFA and MUFA. However, higher intakes of PUFA had no statistical effects on adiposity.Conclusion: These results confirm the notion that high fat diets might lead over time to excess body fat deposition. SFA and MUFA intake also seem to be predictors of actual adiposity markers while high PUFA intake seems to exert no effect on these markers.Sponsorship: This work forms part of a research program supported by the Medical Research Council of Canada (PG-11811).

Obesity: a disease or a biological adaptation?

The increase in obesity prevalence is problematic as this condition is associated with health complications such as diabetes and cardiovascular diseases, more particularly when the excess body fat is stored in the deep abdominal region. On the other hand, obesity facilitates the maintenance of body homeostasis probably because of an increased hormonal gradient which favours the regulation of energy balance, to give but one example. The regulation potential of excess body fat is particularly apparent in the reduced‐obese state where a reduction of energy expenditure, fat oxidation and some immune system markers, as well as an increase in appetite, stress vulnerability and circulating and adipose tissue organochlorines have been observed. These constitute another category of risk factors which can certainly favour the accumulation of body fat to reestablish body homeostasis on other fronts. Under such conditions, obesity is perceived by the physiologist as a necessary biological adaptation rather than a disease. For health professionals, this emphasizes the importance to seek a reasonable compromise between the favourable reduction of risk to develop metabolic complications by body weight loss and the physiological vulnerability which is also generated by such an intervention.