Better understand obesity
An interview with Angelo Tremblay
“Obesity is a fascinating question for the physiologist that I am. It is really the issue of the relationship of individuals with their environment. We had to adjust to maintain different balances in a context (family, work, society) that may have changed too much from what we were willing to tolerate. “
Angelo Tremblay holds the Canada Research Chair in physical activity, nutrition and energy balance1. He is a full professor, at Laval University, in the Department of Social and Preventive Medicine, Division of Kinesiology2. He also collaborates with the Chair on Obesity3. In particular, he heads a research group on the factors that predispose to obesity.
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PASSPORTSHEALTH.NET – What are the main causes of the obesity epidemic?
Pr Angelo Tremblay – Of course, junk food and lack of exercise are involved, but there is also stress, lack of sleep and pollution, for example.
Organochlorine pollutants, such as certain insecticides and pesticides, have been banned, but they persist in the environment. We are all polluted, but obese people are more so. Why? Did the gain in body fat give the body a solution to put these pollutants out of harm’s way? Pollutants indeed accumulate in adipose tissue and as long as they “sleep” there, they are not disturbing. It is a hypothesis.
In addition, when the obese person loses weight, these pollutants become hyperconcentrated, which could cause the gain of weight in someone who has lost a lot of it. Indeed, in animals, a greater concentration of pollutants is associated with several metabolic effects that adversely affect the mechanisms that allow calories to be burned: marked decrease in thyroid hormones and their concentration, decrease in energy expenditure at rest, etc. .
On the sleep side, studies indicate that little sleepers are more likely to be overweight. Experimental data helps us understand why: when you don’t get enough sleep, leptin, a satiety hormone, decreases; while grhelin, a hormone that stimulates appetite, increases.
PASSEPORTSANTÉ.NET – Does a sedentary lifestyle also have an impact?
Pr Angelo Tremblay – Yes quite. When we exercise a sedentary profession, is it the stress of mental solicitation that destabilizes us, or is it the lack of physical stimulation? We have preliminary data which indicates that mental work increases appetite. Subjects who read and summarized a text in writing for 45 minutes ate 200 calories more than those who took 45 minutes of rest, even though they had not expended more energy.
In kinesiology, we have been studying the various impacts of physical activity on our lives for years. How is it that we do not focus more on the effects of mental work, a dimension however much more solicited than in the time of our ancestors?
PASSPORTSHEALTH.NET – What about psychological factors? Do they play a role in obesity?
Pr Angelo Tremblay – Yes. These are factors that we like to cite, but to which we do not give much importance. The stress of great ordeal, death, job loss, great professional challenges that are beyond our capabilities can play a role in weight gain. A study by researchers in Toronto in 1985 found that 75% of obesity cases in adults occurred as a result of a significant disruption in their life trajectory. The results of a study of Swedish children and one in the United States point in the same direction.
However, psychological distress is not decreasing, on the contrary! The current context of globalization increases the demand for performance at all costs and causes many plant closures.
We tend to think that a psychological factor doesn’t change the energy balance, but I think that’s a mistake. A lot of things are interrelated. I wouldn’t be surprised if psychological stress had measurable effects on biological variables that affect food intake, energy expenditure, the body’s use of energy, etc. These are aspects that have not yet been well studied. Of course, some people become obese because of the “lust of everyday life”, but others are because of the “heartache of everyday life”.
PASSPORTSHEALTH.NET – What is the role of genetic factors in obesity?
Pr Angelo Tremblay – It’s hard to quantify, but as far as we know, obesity is not caused by genetic mutations. We have pretty much the same DNA as “Robin Hood”. So far, however, the contribution of the genetics of obesity has focused more on the physical aspects of the person. For example, neuromedin, (a hormone) that was discovered at Laval University, has made it possible to establish a link between a gene and eating behaviors that contribute to obesity. And we may discover other genetic variations in DNA linked to psychological traits leading to overeating.
I think it is very clear that there are some individuals who are more susceptible than others to the current obesogenic environment, and that their susceptibility is partly explained by genetic characteristics that we do not yet have. defined. It’s a shame, but we don’t know exactly what we’re doing. We deal with a problem we do not know very well and, in doing so, we have difficulty finding effective solutions.
PASSPORTSHEALTH.NET – What are the most promising avenues in the treatment of obesity?
Pr Angelo Tremblay – It is very important to better understand and better diagnose in order to intervene better. Obesity is currently a problem which we do not fully understand. And until the therapist is fully aware of what is causing a problem in a given individual, he or she is at high risk of hitting the wrong target.
Of course, it will promote a negative calorie balance. But, what if my problem is being sad, and the only gratification I have left is eating certain foods that make me happy? If the therapist gives me a diet pill, there will be a transient effect, but it will not solve my problem. The solution is not to target my beta-adrenergic receptors with a drug. The solution is to give me more happiness in life.
When a medication works by targeting a certain type of receptor, logic would dictate that this type of abnormality be found in the patient before it is administered. But that is not what is happening. These drugs are used as crutches to compensate for a reality that has not been well characterized. It should therefore come as no surprise that when you stop taking the medication, the problem comes back. It should also come as no surprise that when the medication has given its maximum effect, either after three or six months, the causes of obesity again emerge. We won a small battle, but not the war …
Regarding the dietary approach, you have to manage it with caution. You have to take into account what the person can take care of at a specific time. From time to time, I remind the dietitians I work with to be careful with the machete: drastically cutting certain foods may not be an appropriate treatment, even if these products are not healthy. It is important to make as many changes as possible, but those changes should be compatible with what the person can and wants to change in their life. Our knowledge is not always applicable as it is in certain situations.
PASSEPORTSANTÉ.NET – Is obesity reversible on an individual and collective level?
Pr Angelo Tremblay – It certainly is in part on an individual level, if we look at the successes achieved by the 4 research subjects registered with the National Weight Control Registry.4 the United States. These people lost a lot of weight and then maintained their weight for long periods of time. Of course, they have made some very significant changes in their lifestyle. This requires great personal commitment and the support of a health professional who will be able to make appropriate recommendations.
However, my curiosity remains unsatisfied on certain points. For example, could it be that a significant weight gain could induce irreversible biological adaptations, even if we lose weight? Does a fat cell, which has gone through a cycle of weight gain and loss, turn back into exactly the same cell, as if it had never grown in size? I do not know. The fact that a majority of individuals have great difficulty in losing weight justifies the question.
We can also wonder about the “coefficient of difficulty” represented by maintaining weight after weight loss. Maybe it takes a lot more vigilance and lifestyle perfectionism than the effort that should be put in before you gain weight. This type of argument, of course, leads us to say that prevention is the best treatment, because even successful treatment may not be complete therapy for obesity. It’s a shame, but this possibility cannot be ruled out.
Collectively, let’s be optimistic and pray that the epidemic is reversible! But, it is clear that currently, several factors increase the coefficient of difficulty in maintaining a healthy weight. I mentioned stress and pollution, but poverty can also play a role. And these factors are not declining in a context of globalization. On the other hand, the cult of beauty and thinness contributes to eating disorders, which over time can cause the rebound phenomenon I mentioned earlier.
PASSPORTSHEALTH.NET – How to prevent obesity?
Pr Angelo Tremblay – Have a healthy lifestyle as much as possible. Of course, you can’t change everything or completely metamorphose. The primary goal is not weight loss, but the implementation of changes that promote a negative calorie balance:
-A little walk? Of course, it’s better than nothing.
-Put a little hot pepper5, four times a week in a meal? To try.
-Take skimmed milk instead of a soft drink? Surely.
-Reduce sweets? Yes, and it’s good for other reasons.
When we put into practice several changes of this type, it happens a bit what we were told when we were taught catechism: “Do this and the rest will be given to you in addition. Weight loss and weight maintenance come on their own and it is the body that decides the threshold beyond which it is no longer able to lose fat. We can always cross this threshold, but it risks becoming a battle that we only win for a certain time, because nature risks taking back its rights.
Other leads … Breast feeding. There is no consensus, because the studies differ by their context, their experimental strategy, their population. However, when we look at all the data, we see that breastfeeding seems to have a protective effect on obesity. Pregnancy smoking. The baby who “smoked” is a lower birth weight, but what we also observe is that he is chubby a few years later. So the child’s body “bounced back”. He behaves like a scalded cat, as if he doesn’t want to go back to a small weight. Leptin. It is a messenger of adipose tissue which has satiating and thermogenic effects, that is to say, it reduces food intake and increases energy expenditure a little. Since in obese people there is more leptin circulating, it has been hypothesized that there is “resistance” to leptin, but this has not yet been clearly demonstrated. We have also learned that this hormone influences the reproductive system and may have anti-stress effects. The mini yo-yo of food insecurity. When you have enough to eat for a while and at another time you have to restrict yourself because of a lack of money, the body experiences a yo-yo phenomenon. This mini yo-yo, physiologically speaking, is not favorable to energy balance, because the body has a tendency to “bounce back”. I would not be surprised if some families who are on social assistance experience this kind of situation. Evolution and modern life. The sedentary lifestyle of the modern world has completely called into question the physical activities on which the natural selection of the human species is based. 10 years ago, 000 years ago, you had to be an athlete to survive. These are the athlete’s genes that have been transmitted to us: the evolution of the human race has therefore not prepared us at all to be sedentary and gluttonous! Education by example. Learning to eat well at home and at school is part of a healthy lifestyle to which children must be exposed, just as it is considered important to teach them French and mathematics. It is an essential ingredient of good manners. But cafeterias and school vending machines should set a good example! |
Françoise Ruby – PasseportSanté.net
The 26 September 2005
1. To find out more about Angelo Tremblay’s research projects and the Canada Research Chair in physical activity, nutrition and energy balance: www.vrr.ulaval.ca/bd/projet/fiche/73430.html
2.To find out more about kinesiology: www.usherbrooke.ca
3. The website of the Chair in obesity at Université Laval: www.obesite.chaire.ulaval.ca/menu_e.html
4. National Weight Control Registry : www.nwcr.ws
5. See our new Fruits and Vegetables Take on the Extra Pounds.