Questions have begun to surface about the health benefits of weight reduction by the overweight and obese. Although difficult to achieve, there is sound evidence supporting continuing efforts to achieve this aim because reduced chronic disease and increased longevity are likely to ensue. Consequently, a workshop entitled “Dietary Synergies in Appetite Control” was held to discuss present knowledge of appetite control. The goal was to synthesize what is known in an effort to provide future direction for approaching the problems of overweight and obesity.
The presentations and discussion followed a theme of signals and synergies that occur from the initial thought of eating through processes that occur in the oral, gastric, intestinal, peripheral, and central sites. Examples of signaling systems were identified, but there was consensus that knowledge remains limited on which satiety signals, or combinations of signals, most effectively and consistently reduce food intake and whether this affect can be specifically mimicked by nutrients, foods, and/or drugs. Indeed, still unresolved is the question of whether body weight is actively regulated? If so, how tightly is it controlled, and how do environmental and physiological systems interact to achieve this end. The workshop highlighted several key points. First, the system is complex and must integrate signals from the environment and the orosensory region, gastrointestinal system peripheral tissues, and the brain. Responses to these stimuli ultimately distill down to variations of meal size and intermeal interval. The significance of each was widely debated, but ultimately it is the combination of these two measures that influence the “return to hunger.” Modulation of this sensation is of key importance if we hope to aid individuals in weight management.
The concept that perceptual and physiological controls can be manipulated in the short term to achieve some outcome was documented, but it was also noted that chronic change is difficult. New approaches that employ multiple dietary and behavioral manipulations may aid moderation of positive energy balance. Synergies must be sought between component parts of ingestion-related systems. Is this a real possibility for those attempting weight loss? There are numerous suggestions, both in the literature and anecdotally, that success rates are better than what has been predicted in the past using several different modalities. Insights also emerged on other areas that may be fruitfully targeted for additional research, product development, and/or population recommendations for weight management.
Tonic signals through insulin, leptin, and, perhaps, certain cytokines, amylin, visfatin, and adiponectin secretion can be important in the development of dietary strategies during and after weight loss. Their roles may be key because of their modulatory effects on a wide array of meal-related endocrine and neural signals.
A concept is emerging that hedonic systems, both external and internal, over-ride satiety signals. Verification of this concept and exploration of approaches to address weight management through modulation of reward are warranted. The endocannabinoid system is presently being probed on the pharmacological side, but are there simple and practical behavioral approaches that can be brought into play? Good evidence exists that palatable food can disrupt compensatory responses to meals weakening satiety. Curtailment of variety to reduce the rewarding properties of eating has been a long-standing approach to weight maintenance. Success has been stronger for short-term compared with longer term weight reduction, but given the recent successes of structured diets, it may be worthwhile to revisit this approach.
What role can the food industry play? This meeting did not attempt to comprehensively evaluate the food industry's role in the increasing incidence and prevalence of obesity. However, insights into the approaches and technologies that are being evaluated by one company with interest in weight management were presented. As an example, the ileal brake has been considered a potent feeding inhibitor through slowing of food passage in the gastrointestinal tract and providing satiety signals to the brain. By instilling specific fats or fatty acids into the ileum, measures of satiety are enhanced. It has been suggested that fat in food does bring into play fat-related signaling systems. Fat is an energy-dense, biologically available substrate after consumption, but the fat signaling system can potently inhibit intake.
Often, new ideas are needed to address long-standing problems. Body weight has been increasing for centuries. This suggests a strong bias toward positive energy balance. Appetitive sensations have likely contributed to the trend, and harnessing them may aid its abatement.