If you thought that the stresses of present-picking, turkey-basting and relative-juggling are to blame for weight gain, you are not alone. A Google search for ‘stress and weight gain’ reveals a staggering 32,000,000 sites dealing with the topic. However, researchers from our research group have shown that the effect of stress on weight gain may not be as large as you may have thought.

The body tries to maintain stability by adapting to a change in the environment, a process called homeostasis. Stress can be defined as any external factor, physical or psychological, which threatens to throw the body out of homeostasis. Whether running from a hungry lion, or suffering stage-fright before a speech, the body’s response will be the same: the stressor (lion or stage-fright) will trigger the so called ‘fight-or-flight-response’, which is marked by increased heartbeat, muscle-tension, sweating, dilation of the pupils and the release of the ‘stress-hormones’ adrenalin and cortisol. This response is extremely useful to mobilise resources, help us get through difficult situations and regain homeostasis. However, when we experience the on-going stresses of modern life, such as money-worries, job stress, or social pressures, we begin to feel the strain. Long-term stressors overwhelm the body’s coping system, deplete resources and ultimately lead to exhaustion. It has been thought that weight gain results from the body trying to restore homeostasis by inducing metabolic changes which promote fat storage on the one hand and behaviour changes on the other, for example making less time to be active or reaching for cookies instead of carrots.

Results from studies investigating this topic are mixed – some have found that stress has an effect on weight gain, and others have not. Researchers from our department decided to look at the effect from all these studies overall. Summarizing results of several studies on the same topic to find out the ‘true’ effect is called meta-analysis. The studies that were included in this meta-analysis had to be conducted over a period of time (because these are more accurate than studies that only look at a single time-point), measure weight objectively, and focus on external stressors such as life events, work-or caregiver stress. Fourteen studies from Europe and the USA met the criteria; each ‘stress category’ (life events, work- or caregiver stress) was analysed separately.

Results of the meta-analysis showed that stress is related to weight gain, although the effects were very small. When the researchers looked at the results in more depth, they saw that studies that went on for longer and were of better quality were more likely to show an effect of stress on weight. They also saw that the effect appeared to be stronger in men. It did not matter whether the stressor was related to life or work. Unfortunately, eating behaviour was not assessed, so the researchers could not tell whether it changed under stress.

Although there are not very many studies that looked at the topic over a period of time, and imprecise measurements of stress were often used, the findings are relatively robust because of the way the studies were combined. Finding a stronger link of stress on weight in men complements other findings which show that men have a stronger fight-or-flight response. Overall, however, it can be seen that the effects of stress on weight are much smaller than often made out in the media. Blaming the relatives for a bulging belly might be convenient, but complex issues like weight gain unfortunately have no simple, or convenient, answer.

Source: http://www.nature.com/oby/journal/v19/n4/full/oby2010241a.html

Promoting dieting for weight loss and weight maintenance is often criticized, because of the widely held belief that restricting food intake is the beginning of a slippery slope, leading to overeating and eating disorders.  However, a recent review by our department investigating the literature of dietary restraint shows that this may not be the case.

The idea that restricting food intake would lead to uncontrolled binge eating stems from laboratory studies from the 1970s.  Counter to expectations, people reporting that they were trying to lose weight by eating less (restrained eaters), ate more than unrestrained eaters when offered unhealthy but tasty food after being encouraged to break their diet by drinking a high calorie milkshake.  They also ate more than others after drinking alcohol or when they were upset.  These observations led to the belief that trying to control eating with one’s intellect rather than instinct can lead to less sensitivity to feelings of hunger and fullness, and cause people to overeat when their guard was lowered.  At the same time, research pinpointed dieting as a precursor of eating disorders, such as anorexia nervosa and bulimia nervosa, which further strengthened the lobby against the restriction of food intake.

However, closer examination of the research showed that the methods used to classify people as ‘restrained’ or ‘unrestrained’ eaters may have contributed to the findings.  For example, some of the questions asked to find out whether people restrict their food intake were actually assessing tendencies to eat in an uncontrolled way.  The links between restrictive eating and binge-eating were even less clear when considering the artificial lab setting in which participants were persuaded to break their diet, and then presented with an overwhelming amount of tasty food and told to eat as much as they wanted.

Furthermore, in the current environment, it may well be that a person eats less than desired, but still eats more than would be needed to keep weight stable.  Eating only one chocolate cake is better than eating two, but still, it can hardly be considered beneficial to your health!  This means that measuring food restriction alone may not be such a good indicator of successful weight management.  People who report restricting how much they eat may simply be the ones most likely to overeat.

Support for the positive effects of food restriction comes from real world examples.  In overweight individuals, where overeating is common, restricting food intake is related to lower body weight.  Findings from weight loss studies also show that the people doing best are the ones who vigilantly pay attention to what and how much they eat and don’t binge eat. In fact, evidence from studies with people suffering from binge eating has shown that gaining control over the amount of food eaten is related to fewer binge episodes.

So, how come the myth about the relationship between food restriction and disordered eating behaviour persists? The devil here may be in the detail of how people restrict their food intake. People who are following rigid, rule-based, ‘all-or-nothing’ eating are more likely to react with overeating and disordered eating once their rules are broken than people who take a more flexible approach, limiting rather than totally eliminating certain foods, and compensating for ‘off’ meals at the next meal or with an extra hour at the gym. Identifying oneself as a ‘dieter’ seems to be related to more rigid rules about eating and so may be undermining weight loss efforts.

The key to successful weight management may lie not in restraint per se, but in self-control. The ability to forego immediate rewards in pursuit of higher goals seems to be a skill that, once acquired, is not limited to successful weight management, but extends to other areas of life such as success at work, and better management of time and finances.  Although the capacity to control one’s desires seems to be partly inherited, the good news is that people can also be trained in self-control.  Learning how to control emotions, monitoring and evaluating one’s own  behaviour, setting goals, acquiring more beneficial problem-solving skills and thinking up action plans for resisting temptations have all been shown to enhance self-control.  The view that restraint is always ‘bad’ may need to be revised and the distinction between ‘rigid’ and ‘flexible’ restraint should be given more consideration.

The bottom line is that exercising a little restraint may not only benefit your weight but also your wallet, as long as it does not turn you into a rigid, miserly and overly concerned kill-joy.

Article Reference: Johnson, F., Pratt, M., Wardle, J. (2011). Dietary restraint and self-regulation in eating behavior. Int J Obes (Lond) doi:10.1038/ijo.2011.156.