What is it that drives some of us to eat foods that we know aren’t good for us? Lot’s of things, perhaps, but one thing I have found to be consistently the most important factor overall is plain old hunger. For me, keeping one’s appetite from running out of control is a core strategy for healthy eating. Once we get too hungry, it’s almost impossible to make healthy food choices, pure and simple.
I was lecturing on Monday in a slot just before lunch. At about 1.00 pm I put up a picture of a glazed doughnut. I suggested to the audience that if this image was stimulating intense desires for the doughnut, then the chances are they’ve allowed themselves to get too hungry. About 15 minutes later the audience was going to be faced with a wide range of foods at lunch, many of which would be unhealthy but difficult to resist if hunger had bitten hard.
The same day saw the publication of a study that provides some insight into the neurological and biochemical basis for what happens to people’s resolve when they get hungry . In this study, individuals underwent scans assessing brain activity (functional MRI) while being presented with pictures of a variety of foods, including high-calorie ones. This situation was repeated in two settings:
- when individuals had normal blood sugar levels
- when individuals had low blood sugar levels
When blood sugar levels were low, there was activation in parts of the brain (limbic-striatal regions) that drive the desire for food.
However, when blood sugar levels were normal, at least some of the subjects saw activation of other parts of the brain (medial prefrontal cortex), which ultimately reduces the drive to eat. In obese subjects, this control mechanism appeared to be absent, though.
In short, what this study shows is that obese individuals may lack brain responses that put a natural brake on our desire to eat highly calorific foods. It also shows that allowing blood sugar levels to drop (which can happen if we go for too long without food) really does tend to make life difficult for those keen to eat a healthy diet.
I’ve found in practice that many overweight individuals keen to shed pounds actually welcome hunger. At the back of their minds, many are thinking perhaps ‘I am hungry, I must be in calorie deficit and therefore must be losing weight’. They might be right. But, the problem is what happens later when faced with food and the overwhelming urges they may have to eat none-too-healthy fare. It’s been my view for a long time that if someone wants to control their weight sustainably, hunger is the enemy.
1. Page KA, et al. Circulating glucose levels modulate neural control of desire for high-calorie foods in humans. Journal of Clinical Investigation epub 19 September 2011