Why Men Are Better Dieters Than Women

  • Share
  • Read Later
Ansgar / zefa / Corbis

You wouldn't think a diet would be a cause of marital discord. But it often is — at least when couples try to shed pounds together and, as often happens, the husband drops the weight a lot faster than the wife does. Well, guess what, guys? It's not your steely resolve or your trips to the gym or your superior genes that are entirely behind it. It might just be your brain.

It's hardly a secret that men and women gain weight, lose weight and think about weight entirely differently. It's also not news that body-fat percentage alone — with females naturally carrying an extra ladling of adipose tissue — gives males a head start in the slimming game. But a new study from Brookhaven National Laboratory looked deeper into the primal ways in which we react to the very presence of food — and if you like to eat, this is not a study you would have wanted any part of. (See the Year in Medicine 2008.)

Nuclear-medicine specialist Dr. Gene-Jack Wang first recruited a group of 23 male and female volunteers — none of whom were obese and all of whom were in good general health — and instructed them to fast for 17 hours. During that period, he and his team interviewed them about their favorite foods and asked them to rank each on a 1-to-10 scale. The researchers then selected one food for each subject, the only requirement being that it scored 7 or above in desirability. When the 17 hours were up, the volunteers were injected with a nuclear tracer, placed in a brain-imaging PET scanner and presented with a food they craved. Actually, they were more than merely presented with it.

"If you said you liked barbecued ribs, we'd put a big portion of them in front of you," says Wang. "We'd warm them in a microwave first so you couldn't get away from the smell, and we'd give you a cotton ball with a bit of the food on it so you could taste it. Then we'd have one of the nurses describe how the food was made." (See pictures of what makes you eat more food.)

When a hungry person is hit with such multisensory stimuli, it's no surprise that the brain starts screaming chow time, and the PET scan showed that it was screaming loudly. Appetite and hunger are processed in a lot of regions — most notably the orbital frontal cortex, which is linked to self-control; the striatum, which is linked to motivation; the hippocampus, which is linked to memory; and the amygdala, which is linked to powerful emotions. In Wang's subjects, all these regions were ringing the dinner bell.

Wang then told his volunteers to do what few mortal people could do: think about something else. For the next 40 minutes, while the PET scanner hummed, the subjects fought to close their minds to the thoughts of food in any way they could, though they were required to keep their eyes open. "We tried to make it a real-life experience," says Wang. "It's like being in a buffet line, only it lasts a lot longer." (See the top 10 food trends of 2008.)

When the scans were studied and the results were tallied, it appeared that both sexes were actually able to lower the overall sensation of hunger. In most people, the brain may grow partially habituated to an empty belly over time, and all of Wang's volunteers did a good job of hastening that desensitization. What the men could do that the women couldn't was quit ruminating on food, successfully suppressing — if only temporarily — the conscious desire to eat. The women continued experiencing emotional cravings even if their hunger had subsided.

Wang is not certain what's behind the differences, though he suspects hormones may play a significant role. He did get a better sense of the areas of the brain those hormones affect most, owing to the fact that he used a long-running PET scan rather than a shorter session with a functional magnetic resonance imager (fMRI), which is how such studies are usually conducted. This afforded him a good look at the amygdala, the deepest and most primitive of the brain structures involved. When the amygdala acts up, it's exceedingly hard to bring it to heel, as anyone suffering from anxiety conditions like phobias or obsessive-compulsive disorder could attest. That the men in Wang's study had some success disciplining their amygdalas was an undeniable accomplishment, but it was one that required enormous effort.

"It takes a lot of inhibition to control the amygdala," says Wang.

That, no doubt, is why even the most resolute dieters — both male and female — so often fail, eventually pouncing on the barbecued ribs. While that does nothing for your waistline or your cholesterol count, it may, briefly, mean more peace in your marriage. At least until the next diet begins.

Read "A Brief History of Veganism."

See "9 Kid Foods to Avoid."