Factors Affecting Ingestive Behaviour: Physiological or Homeostatic Factors
Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we now turn to the some of the factors that can affect ingestive behaviour: Physiological or Homeostatic Factors In contrast to excess caloric consumption that results largely from environmental determinants, over‐eating in response to increased hunger or reduced satiety can be viewed as a physiological response to a perturbation of the homeostatic system and is perhaps best termed homeostatic hyperphagia. Primary homeostatic hyperphagia can result from genetic defects in the homeostatic system (e.g. leptin deficiency, melanocortin type 4 receptor mutation or Prader Willi Syndrome) and are rare. Secondary homeostatic hyperphagia can result from acquired defects or perturbations in the homeostatic system (e.g. head trauma, craniopharyngeoma, insulinoma). Tertiary homeostatic hyperphagia, by far the most common category, is largely the result of inappropriate feeding intervals and/or nutrient selection. Thus, skipping meals, resulting in a compensatory hyperphagic response (rapid ingestion of energy‐dense foods), is perhaps the most prevalent form of homeostatic hyperphagia. Ingestion of high‐glycemic foods resulting in a rapid rise and fall in blood glucose and insulin levels (‘crash and crave’) may prompt increased snacking and overconsumption, although this notion remains controversial. Meal duration and composition can also affect satiety response, whereby delayed or reduced satiation (e.g. in response to hasty eating, energy‐dense foods, low fibre intake, liquid calories) can result in excess caloric intake. The presence of homeostatic hyperphagia (characterized by over‐eating in response to increased hunger and/or reduced satiety) will likely call for interventions that specifically address the underlying perturbation in this system (e.g. administration of leptin, excision of the insulinoma, correction of meal pattern, nutritional hygiene, portion control, etc.). Patients with obesity resulting from tertiary homeostatic hyperphagia are the most likely to benefit from dietary counselling. @DrSharma Edmonton, AB
The Canadian Obesity Network Is No More – Long Live Obesity Canada!
Over a decade ago, together with over 120 colleagues from across Canada, representing over 30 Canadian Universities and Institutions, I helped found the Canadian Obesity Network with the support of funding from the Canadian National Centres of Excellence Program. Since then the Canadian Obesity Network has grown into a large and influential organisation, with well over 20,000 professional members and public supporters, with a significant range across Canada and beyond. During the course of its existence, the Network has organised countless educational events for health professionals, provided training and networking opportunities to a host of young researchers and trainees, developed a suite of obesity management tools (e.g. the 5As of obesity management for adults, kids and during pregnancy), held National Obesity Summits and National Student Meetings. raised funds for obesity research, the list of achievements goes on and on. Most importantly, the Network has taken on important new roles in public engagement, voicing the needs and concerns of Canadians living with obesity, and advocating for better access to evidence-based prevention and treatments for children and adults across Canada. To better reflect this expanded mission and vision, the Board of Directors has decided to convert the Canadian Obesity Network into a registered health charity under the new name – Obesity Canada – Obésité Canada. So with one sad eye, I look back and hope that the Canadian Obesity Network rests in peace – Long Live Obesity Canada! @DrSharma Edmonton, AB
Factors Affecting Ingestive Behaviour: Socio-Cultural Factors
Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we now turn to the some of the factors that can affect ingestive behaviour: A wide range of socio‐cultural and environmental factors can determine changes in ingestive behaviour. Thus, traditions or habitual patterns, belief systems, peer pressure, availability of foods, and the context in which these are presented and consumed can all significantly predispose to or prompt increased caloric consumption. Moving to a neighbourhood with more fast food outlets, exposure to food advertising, decreasing affordability of healthy foods, or increased professional or social pressure can all influence eating behaviour. Thus, for example, taking up a job that requires extensive wining and dining of clients is likely to increase caloric consumption. Similarly, regularly partaking in social activities that revolve around eating and drinking can promote caloric excess. Not surprisingly, the frequency of eating out is an important determinant of food quality. As many of the factors that influence overconsumption are subtle (e.g. plate size, food variety, ambient distractions, etc.) and do not generally involve conscious decision‐making, exposure to an environment that promotes ‘mindless’ overeating will promote weight gain. For individuals in lower socioeconomic class, affordability and availability may limit access to a healthy nutritious diet. Lack of knowledge about healthy eating may also contribute. When present, identifying, recognizing and acknowledging the possible role of the socio‐cultural factors that promote overconsumption or pose important barriers to eating a healthy, calorically balanced diet is the first step to devising strategies to mitigate these influences or overcome these barriers. In addition to nutritional counselling patients in whom strong socio‐cultural determinants of obesity are identified may benefit from counselling by a social or public health worker. Commentary: as important as socio-cultural factors may be, they are by far not the only factors affecting ingestive behaviour – more on this in coming posts. @DrSharma Edmonton, AB
Etiological Assessment of Obesity: Factors Affecting Ingestive Behaviour
Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we now turn to the some of the factors that can affect ingestive behaviour. Once you have quickly established that weight gain is not primarily driven by a change (decrease) in metabolic requirements, you turn to the most likely cause of weight gain – eating more calories than your body actually needs: Ingestive behaviour, which includes both eating and drinking, accounts for 100% of total energy intake. In contrast to total energy expenditure, caloric intake (on a daily basis) can vary from zero (fasting) to several times that of total energy requirements (e.g. during a binge eating episode). Given the ease with which it is possible for energy intake to exceed caloric expenditure, it is therefore not surprising that caloric hyperalimentation is a major determinant of weight gain. Any assessment of obesity or increase in body weight thus requires a careful assessment of ingestive behaviour. Evidence for caloric hyperalimentation or hyperphagia should in turn prompt systematic exploration of the determinants of this behaviour. In this context, it helps to view over‐eating as a symptom of an underlying perturbation of ingestive behaviour rather than simply a wilful behavioural choice. While the socio‐psycho‐neurobiological determinants of ingestive behaviour are exceedingly complex, in clinical practice, it is possible to divide them into four domains: socio‐cultural factors, biomedical or physiological (homeostatic) factors, psychological (hedonic) factors and medications. In a given individual, these domains are intimately connected and show considerable variation and overlap. Nevertheless, in practice it is often possible to determine the primary domain that explains the excess caloric intake in a given individual and can thus provide the key to developing a treatment plan that addresses the root cause of this behaviour. More on the various factors affecting ingestive behaviour in coming posts. @DrSharma Edmonton, AB
Factors Affecting Energy Metabolism: Brown Fat, Medications, Weight Loss
Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we now turn to the some of the factors that can affect metabolic rate: Metabolically Active Fat Recent evidence suggests that brown adipose tissue (BAT) exists into adult hood and can, when present account for as much as 20% of daily resting energy expenditure. While the exact contribution of BAT (or lack thereof) to obesity remains to be determined, the presence and inducibility of BAT by cold exposure is inversely related to BMI, appears higher in women, and diminishes with aging. Given the role of cold exposure in the expression of BAT, it can be speculated that an increase in ambient temperature may promote weight gain by significantly reducing BAT and, thus, metabolic rate in some individuals. In rodents, increased production of neuropeptide Y in the hypothalamus can not only increase food intake but also reduce energy expenditure via a reduction in non‐shivering thermogenesis in BAT and facilitate triglyceride deposition through increased insulin levels. Medications A wide range of medications can affect metabolic rate. Notably, the use of beta‐blockers has been shown to significantly reduce thermogenesis, resulting in clinically relevant weight gain 34. Metabolic rates can also be reduced by the discontinuation of drugs that promote thermogenesis such as beta‐adrenergic agents, stimulants (including performance‐enhancing and illicit drugs like crack/cocaine), coffee or nicotine, resulting in weight gain.\ Weight Loss Finally, weight loss can markedly reduce energy requirements with a 5–10% reduction in body weight reducing resting metabolic rate by as much as 20% in some individuals, thereby substantially increasing the susceptibility to weight regain in the post‐obese state. Commentary: In summary, any of the many factors that can reduce metabolic rate, can result in weight gain even with no change in energy intake or energy expenditure. In a clinical setting, this would apply to the patient, who tells you that they have not changed their food intake or their activity levels and, yet, have gained weight. Rather than simply discarding this information from a patient as being untrue or “delusional”, clinicians should give careful consideration to the factor that there very well may be factors that have led to a significant reduction in metabolic requirements. @DrSharma London, ON
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