1 Myths, Presumptions and Facts about Obesity Cátia Martins Associate Professor Medical Faculty, IKM NTNU Researcher RSSO St. Olavs Hospital
2 Myth believe held true despite the existence of substantial refuting evidence. Presumption - believe that is held to be true, but for which convincing evidence does not yet exist to confirm or to disconfirm their legitimacy. Fact - proposition backed by sufficient evidence to consider them empirically proved for practical purposes.
3 The link between obesity and health Characteristics of obese individuals Causes of obesity Obesity treatment strategies
4 1. Body weight is a measure of good health McAuley & Blair, 2011 (J Sports Sci); Salas, Forhan & Sharma, 2014 (Clin Obes)
5 2. Obese people are less physical active Overweight and obese children tend to have similar PA levels (MVPA/day duration) as their normal weight conterparts Obese adults may have lower PA levels than normal weight controls, but not necessarily lower PA energy expenditure Obese individuals spend more energy for the same volume of exercise compared with normal weight controls, particularly for weight bearing exercise Is physical inactivity a cause or a consequency of obesity?! Salas, Forhan & Sharma, 2014 (Clin Obes)
6 2. Obese people are less physical active
7 3. All obese people eat unhealthy diets The nutritional quality of the diets consumed by obese individuals is not significantly different from that of normalweight individuals Obese individuals may consume healthy or unhealthy diets, as their normal weight peers! But they eat larger amounts of food overall Salas, Forhan & Sharma, 2014 (Clin Obes)
8 4. Obese people lack motivation and self-control Restraint and disinhibition levels between obese and normal weight do not support the notion that obese lack will power or self-control But given the high rate of recidivism in weight loss effords most obese patients lack the motivation to re-engage in new weight loss efforts Salas, Forhan & Sharma, 2014 (Clin Obes)
9 5. Obese people have a low/slow metabolism - Low resting metabolic rate (RMR) - Hypothyroidism Basis for conjecture: - There is an inverse correlation between free thyroxine (ft4) values and BMI - Hypothyroidism causes weight gain and a decrease in RMR and thermogenesis - Free fat mass (FFM) is the main determinant of RMR and obese individuals have a lower % FFM as compared to normal-weight individuals BUT
10 5. Obese people have a low metabolism - Low resting metabolic rate - Hypothyroidism Resting metabolic rate increases progressively with body weight. Obese individuals (as a group) have a higher overall RMR compared with normal-weight (but a lower RMR/kg body weight!) The majority of obese people do not suffer from hypothyroidism Hypothyroidism leads only to minor weight gain
11 6. Snacking contributes to weight gain and obesity. Basis for conjecture: Snack foods are presumed to be incompletely compensated for at subsequent meals, leading to weight gain But. Observational studies also do not shown a consistent association between snacking and obesity or increased BMI. RCTs have produced contradictory results Casazza et al, 2013 (NEJM)
12 7. Regularly eating (versus skipping) breakfast is protective against obesity. Basis for conjecture: Skipping breakfast purportedly leads to overeating later in the day But obese people tend not to eat breakfast Cause or effect?! But the available evidence from RCTs is insufficient to make causal claims about skipping breakfast itself independently affecting obesity. Those successful in maintaining weight loss in the long-term eat breakfast regularly Casazza et al, 2013 (NEJM)
13 8. Small sustained changes in EI or EE will produce large, long-term weight changes. Basis of conjecture: National health guidelines and reputable websites advertise that large changes in weight accumulate indefinitely after small sustained daily lifestyle modifications Whereas the 3500-kcal rule predicts that a person who increases daily energy expenditure by 100 kcal by walking 1 mile (1.6 km) per day will lose more than 50 lb (22.7 kg) over a period of 5 years, the true weight loss is only about 10 lb (4.5 kg), assuming no compensatory increase in caloric intake, because changes in body weight alter energy requirements... Casazza et al, 2013 (NEJM)
14 9. Losing weight quickly will predispose to greater weight regain relative to losing weight more slowly. Basis for conjecture: reaction to the adverse effects of nutritionally insufficient VLCDs (<800 kcal per day) in the 1960s; but the belief has persisted, and has been repeated in textbooks and recommendations from health authorities Several reviews and meta-analysis have shown that a greater initial weight loss is associated with a better weight loss maintenance in the long-term Casazza et al, 2013 (NEJM)
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16 10. Setting realistic weight loss goals in obesity treatment is important because otherwise patients will become frustrated and lose less weight Basis for conjecture: unrealistic goals may undermine the patient s perceived ability to attain goals and lead to descontinuation of lifestyle changes needed for weight loss No inverse association as been found between ambitious goals, program completion and weight loss Some studies have found that more ambitious goals are associated with better weight loss outcomes. Casazza et al, 2013 (NEJM)
17 11. Assessing stage of change or diet readiness is important in helping patients who pursue weight loss treatment to lose weight Basis of conjecture: Patients who feel ready to lose weight are more likely to make the required lifestyle changes Readiness does not seem to predict the magnitude of weight loss or treatment adherence among those who undergo lifetsyle interventions or bariatric surgery Casazza et al, 2013 (NEJM)
18 12. Eating more fruits/vegetables will lead to weight loss or less weight gain, regardless of whether one intentionally makes any other changes to one s behavior or environment Basis of conjecture: By eating more fruits and vegetables (with low energy density), a person would eat less of other foods, with a resulting overall reduction in energy intake. Few RCTs with body weight as an outcome and in which subjects were instructed to simply eat more F&V. Most show no effect. Consumption of fruits and vegetables has several health benefits. However, without other behavioral changes, an increase in the consumption of fruits and vegetables, may result in no weight change or even weight gain Casazza et al, 2013 (NEJM)
19 13. Drinking more water will reduce energy intake and will lead to weight loss or less weight gain, regardless of whether one intentionally makes any other changes to one s behavior or environment. Basis for conjecture: Water is a better choice for weight management than are caloric beverages. The belief that water consumption reduces hunger, enhances satiety, reduces energy intake, and thus promotes weight loss. Evidence is contradictory The belief that drinking water before each meal can affect hunger and food intake could be at least part of an explanation for any effects seen. More research is needed. Casazza et al, 2014 (CRFSN)
20 14. Provision of meals and use of meal replacement products promotes greater weight loss More structure regarding meals is associated with greater weight loss, as compared with holistic programs that are based on concepts of balance, variety, and moderation Casazza et al, 2014 (NEJM)
21 Look AHEAD study Intensive lifestyle intervention: - Hypocaloric diet (1200-1800) <30% energy from fat <10% saturated fat -Liquid meal replacement plan (breakfast + lunch) - Exercise - Behavioural intervention Wadden et al, 2009 (Obesity)
22 15. Daily self-weighing is detrimental for weight management Basis for conjecture: for a person trying to lose weight, seeing his/her weight go in the direction opposite to their efforts can be discouraging. But several experimental studies have shown that daily selfweighing, on its own, produce a significant weight loss People who weight themselves daily are more likely to succeed at losing weight, maintaining their weight after weight loss treatment and preventing weight regaining than those who do not weigh themselves daily Casazza et al, 2014 (CRFSN)
23 16. Weight cycling (i.e., yo-yo dieting) increases the mortality rate. Basis for conjecture: In observational studies, mortality rates have been lower among persons with stable weight than among those with unstable weight Findings are probably due to confounding by health status Recent studies find no compelling evidence that weight cycling, defined in terms of intentional weight loss followed by regain, is associated with excess mortality risk Long-term RCT are unavailable and unethical to perform but studies in animal models do no support the epidemiological association Casazza et al, 2013 (NEJM); Casazza et al, 2014 (CRFSN)
24 What to do then? Myths should be abandon Presumptions should be tested whenever possible with the golden standard procedure: RCT We (health professionals and the scientific community) need to be open and honest about the real state of our knowledge!
25 References: Salas, Forhan & Sharma, Clin Obes, 2014; 4:189-196 McAuley & Blair, J Sports Sci, 2011; 29(8): 773-82 Casazza et al, NEJM, 2013; 368 (5):446-454 Casazza et al, Crit Rev Food Sci Nutr, 2014, in press Wadden et al, Obesity, 2009; 17(4): 713-22***
26 Why do we think and/or claim we know things that we actually do not know? QUESTIONS?