Following the post “I get fat when I exercise is that normal” I have come across some interesting articles that introduce some rather unexpected scapegoats for my weight gain. The first two were the effect of pack size and the most recent one (found via friendfeed user laura) is mental activity, or Knowledge Based Work (KBW) as they call it in the article.

Health professionals and scientists generally consider that the increase in obesity prevalence in our community is attributable to changes in the way of living over the last decades. These changes pertain to the evolution of food habits and also to the progressive increase in sedentariness, which has been promoted by a modern lifestyle.

What I keep wondering is this: is more exercise the best approach to fight the obesity-epidemic, isn’t it eating habit’s we should focus on ? My personal experience is that increased exercise does not necessarily mean less body fat, (because exercise influences my eating habits negatively). In this paper the authors show results suggesting that KBW promotes excess energy intake and thus, another variable on eating habits is introduced.

This study showed that KBW acutely induces an increase in spontaneous energy intake, and promotes an increased fluctuation in plasma glucose and insulin levels. This study contributes to the documentation of a new risk factor for a positive energy balance, with the potential to lead to overweight in the long-term.

They note that an explanation for these effects of KBW is that the brain relies solely on sugar for energy, while exercise also can utilize fat.

This switch in the macronutrient oxidation profile can be realistically considered as a potential cause of the suspected effects of KBW on energy intake.

The authors also note however that eating more does not result from an increased sense of hunger. If I interpret them correctly, you are basically eating more without noticing:

Taken together, these observations suggest that activities requiring a significant cognitive demand favor an overconsumption of foods, without increased feelings of hunger, which could result in body weight gain as a possible long-term outcome.

The answer I guess is not to think less, but of course to eat less. The challenge you face is to eat less than your brain tells you to, and that challenge it seems, is a tougher one for those doing knowledge based work. In my experience this is also a challenge when you exercise. Exercise however, most certainly induces an increased feeling of hunger, – and if one can generalize based on my example, this lends support to the authors notion that exercise and KBW utilizes different energy depots.

Overall, I find the paper very interesting and there is no question that their results go to show that the overweight-epidemic we are seeing in the western world most probably is caused by a complex set of factors influencing eating habits. Exercise I believe, may turn out to be not that important after all.

And that, obviously, is food for thought.

ref: Glycemic Instability and Spontaneous Energy Intake: Association With Knowledge-Based…Chaput et al. Psychosom Med.2008; 70: 797-804