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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

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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

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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

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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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Factors Affecting Energy Metabolism: Sarcopenia

Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we continue discussing factors that can affect metabolic rate: Sarcopenia The importance of fat-free mass as the key determinant of resting metabolic rate, even in a very obese individual [sic], cannot be over emphasized. Obese individuals [sic] can present with wide variations in lean body mass, almost entirely accounted for by differences in skeletal muscle mass. Thus, any change in muscle mass can markedly affect basal energy requirements. In this context it is important to remember that in ambulatory individuals, the mass of weight‐bearing muscles is directly proportional to BMI, as heavier individuals require a greater skeletal muscle mass to support and move their excess weight. This alone accounts for much of the higher basal and activity‐related energy requirements of larger individuals. Although inactivity may be the most common cause of decreased skeletal muscle mass and reduced basal metabolic needs in obese individuals [sic], it is important to consider other causes of muscular atrophy that can likewise markedly reduce energy demands. A wide range of nutritional, neuromuscular, endocrine, renal, cardiac, pulmonary, inflammatory, infectious or neoplastic conditions can result in muscular wasting and sarcopenia. Reduced skeletal muscle mass and weight gain is also noted after many cancer treatments, although the mechanisms remain unclear. Any reduction in skeletal muscle mass not accounted for by a decrease in physical activity and ambulation should prompt investigations for other causes of muscular wasting. Commentary: Sarcopenic obesity is perhaps even more prevalent than most people may think – especially in people who have slight overweight or even moderate obesity. It is particularly common in certain ethnic groups such as South Asians, even at “normal” BMIs. Clinically, this is where body composition studies can be helpful. Although a reduction in muscle mass does reduce resting metabolic rate (RMR), it is important to remember that overall skeletal muscle only accounts for about 15% of RMR. This is why, the notion that building up muscle mass will help with weight loss by burning more calories is not really an effective weight loss strategy. @DrSharma Edmonton, AB

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Factors Affecting Energy Metabolism: Neuroendocrine Factors

Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we continue discussing factors that can affect metabolic rate: Neuroendocrine Factors Across the entire age continuum, a wide range of neuroendocrine factors can not only affect metabolic rate, but also substrate partitioning and utilization, which may directly or indirectly contribute to weight gain. The latter point is of particular significance as low rates of fat oxidation are associated with an increased risk of weight gain. A wide range of neuroendocrine hormones and biomarkers can affect energy metabolism; sympathetic nervous system activity and thyroid function are two major factors directly influencing resting energy expenditure. Sympathetic nervous activity is also a major determinant of post‐prandial thermogenesis and the thermogenic response to a glucose load has been shown to be significantly lower in obese [sic] individuals, a finding that persists even with substantial weight loss. Specific examples of endocrine hormones that affect energy metabolism and substrate partitioning include cortisol, growth hormone (GH) and testosterone. Catabolism associated with hypercortisolism or Cushing’s syndrome can reduce energy requirements and increase the deposition of truncal fat. Discontinuation of GH treatment at the end of childhood growth in individuals with GH deficiency markedly increases fat mass and decreases metabolic rate, whereas GH treatment in GH‐deficient adults has beneficial effects on protein metabolism, energy expenditure and thyroid metabolism. Testosterone deficiency can also result in abnormal energy partitioning, which adversely alters anabolism and reduces metabolic rate. It is important to note that a careful history and physical examination should precede any endocrine testing for these disorders, as testing should be reserved for patients with an above‐normal pretest probability for one of these conditions. Commentary: as pointed out in the last paragraph, while all of the above are important considerations, each one is quite rare, which is why it is important to use clinical judgement in recognising  these factors, rather than simply ordering a battery of endocrine tests on every patient. @DrSharma London, ON

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Factors Affecting Energy Metabolism: Genetics, Sex, and Aging

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: Genetics Because heritable factors appear to be responsible for 45–75% of the inter‐individual variation in body mass index (BMI), the potential impact of genetic determinants of metabolic rate upon the predisposition to obesity must be considered. While numerous somatic and mitochondrial genes with potential effects on metabolic rate have been identified, their contribution to human obesity has yet to be defined Likewise, although there is preliminary evidence for intrauterine and perinatal programming of genes involved in energy metabolism, their role in human obesity remain unclear. What is apparent is that the genetic predisposition to obesity (including both energy intake and metabolism) is not explainable on the basis of a small number of common mutations exerting substantial effects on the individual tendency to weight gain. Thus, a great deal of work is still required before investigation into the multitude of genetic determinants of body weight can potentially impact clinical management. Currently, a careful clinical assessment of family history of obesity and related risk factors remains the best measure of genetic risk for obesity. Sex There is a clear effect of gender [sic] on metabolic requirements, whereby, for the same BMI, women consistently display lower metabolic rates (approximately 20% less) than men, largely accounted for by differences in fat‐free mass (FFM). Aging Aging is an important determinant of a decline in metabolic rate, with an estimated reduction of around 150 kcal per decade of adult life. Factors that result in the age‐related decline in energy requirements include changes in neuroendocrine factors (e.g. sympathetic activity, thyroid function, etc.) as well as a reduction in skeletal muscle quantity and quality (resulting from reduced physical activity, reduced protein intake and other less‐well‐understood factors). Additional factors that can affect metabolic rate will be discussed in subsequent posts. @DrSharma Edmonton, AB

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A Low Metabolic Rate Will Predispose You To Obesity

Continuing with citations from my article in Obesity Reviews on an aeteological framework for assessing obesity, we now turn to the importance of metabolic rate: Any assessment of obesity should begin with an estimate of energy requirement – specifically recognizing that any decrease in metabolic rate, without a corresponding decrease in energy intake and/or increase in activity will result in weight gain. Thus, in anyone presenting with weight gain, without any notable change in energy intake or activity levels, it is safe to assume that the only explanation can be a reduction in energy metabolism. As a rule of thumb: the lower the total energy requirements, the greater the risk of obesity (simply stated: over‐eating is less likely for someone who needs 4000 kcal d−1 than for someone who needs 1500 kcal d−1). In sedentary individuals, resting metabolic rate is responsible for dissipating the vast majority of daily ingested calories (60–75%) and is therefore a key determinant of energy expenditure. Thus, even a small, sustained percentage reduction in resting metabolic rate, without a compensatory adjustment of energy intake or activity, can account for a large cumulative caloric excess over time (e.g. an unbalanced 3% reduction in resting metabolic rate in an individual with a total energy expenditure of 1800 calories can lead to a caloric excess of 32.4 kcal d−1, which can translate into 972 kcal excess per month). Numerous factors can determine and/or affect metabolic rate. These include genetic and epigenetic factors, gender, aging, neuroendocrine function, sarcopenia, metabolically active fat, certain medications and prior weight loss. Commentary: of course the numeric relationship between caloric intake and weight gain is not as straightforward as many people may think. This is because changes in caloric balance will in turn change caloric expenditure – remember, we are dealing here with physiology, not physics! Thus, a 20 kcal daily excess will only lead to weight gain until the higher body weight uses up the extra 20 kcal to maintain itself, at which point the 20 kcal are no longer in excess of demands and a new caloric balance is found (weight-gain plateau – the reverse happens with caloric restriction). Thus, to continue gaining weight, one has to continue increasing caloric intake to ensure that they stay above actual requirements. This self-limiting nature on the effect of a change in caloric intake (increase or decrease) on weight gain is often forgotten when people make simplistic assumptions that small increases in caloric intake… Read More »

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