Here’s a topic I have far too much experience with: trying to control one’s personal mass. Let me lay out my own history…
December, 1979. After two years of university, eating far too many pizzas and far too much vending-machine food, I return to Canada weighing 265 pounds. Nobody calls me “Slim.”
July, 1981. After a year and a half of eating Mom’s cooking instead of fast food, I’ve dropped 30 pounds.
June, 1987. Following several gruelling months of serious dieting and exercise, I’ve reached the incredible (for me) weight of 190 pounds…my weight for the rest of my life, I figure.
October, 1988. I move to Regina. I’m entirely responsible for feeding myself. Disaster awaits.
Present Day. Let’s talk about June, 1987, some more, shall we?
Yes, I’m once again struggling to keep my weight down. And I’m not alone. It seems like everyone weighs more than they think they should…and statistics show that they’re right. U.S. studies indicate that in that country, fully one-third of the population qualifies as “obese,” which, medically speaking, means they weigh at least 20 percent more than they should.
And yet, there’s another segment of the population that seems to be able to eat whatever it wants and doesn’t gain at all–or at least not as much as those of us who aren’t lucky enough to belong to that segment. So what gives?
Scientists may just have an inkling of part of the reason–but first, a bit of background on obesity in general.
Humans gain weight for one reason: they take in more potential energy, in the form of food, than they expend. Everything we do, even sitting quietly and thinking, expends energy, so we’re always burning calories. (A calorie–properly called a kilocalorie–is the energy required to raise the temperature of one litre of water one degree Celsius.) But sitting quietly and thinking doesn’t expend a lot of energy, so if that’s all you do, while continuing to chow down on a pizza a day, you will gain weight–guaranteed. That’s because, as a survival mechanism, the human body stores excess calories against a future day when maybe there won’t be as many calories available. It does that by turning calories into fat.
In particular, it does that by turning excess fat into fat…which is why fat adds taste to food. Through most of our history, there hasn’t been a lot of fat in our diet, so the body had to manufacture fat from the carbohydrates in the grains and other plant products we mostly ate. The body’s not very good at this; it’s much better at turning fat in the diet into fat in the body. As a result, we’ve been genetically programmed to like fatty foods.
One reason that some people remain slim while eating huge quantities of food is that they’re eating food with less fat in it. Studies show that obese people who are eating, say, 3,000 calories a day, can continue to eat 3,000 calories a day but lose quite a bit of weight if those 3,000 calories no longer contain much fat. (However, low-fat isn’t the same as no-fat; your body requires some fat to work properly, so a diet with no fat can also result in weight gain as the body desperately manufactures as much fat as it can from carbohydrates.)
Of course, overeating or eating the wrong sorts of foods is only side of the weight control equation. The other is exercise–or lack of it. Even those of us who are large-boned (if you know what I mean) eat less than our ancestors did at the turn of the century–and yet they were far less likely to be obese. Technology has made the difference. We don’t have to chop wood in the morning to get the stove going. We don’t have to haul water in buckets from the well or the river several times a day. We don’t have to walk behind a plow all day. Heck, we don’t even have to get up off the couch to change channels on the TV any more! As a result, our daily food-energy requirement is rather slim–and we aren’t.
However, there’s still one other component to weight control, and it’s the one that’s currently in the news: the genetic component. No big surprise that adopted identical clones–er, twins–tend to share a body type between them that is different from that of their adoptive parents. Scientists estimate that a quarter to a third of the mix of elements that go into determining our weight is genetic.
Just a few days ago, Craig Warden, an edocrinologist at the University of California, Davis, reported the discovery of a gene called UCP2, or uncoupling protein 2, in mice. This gene determines whether calories are burned off and turned into body heat, or stored as fat. A similar gene, called UCP1, was found a couple of years ago, but that gene occurred only in brown fat–and although other animals have lots of brown fat, humans have very little. However, a version of the new gene (at least 95 percent identical to the one in mice) exists in almost every tissue in the human body, including muscle and white fat.
In some mice, this gene is more active than in others. If the human gene works the same way, it might explain why two people can eat similar high-fat meals and perform similar physical activity, but only one of them gains weight.
In the experiments that revealed the action of UCP2, a special strain of mice prone to obesity and a strain that tends to be thin were put on identical high-fat diets. The mice prone to obesity gained twice as much weight as the other mice over the next few months, and tests showed that their UCP2 was much less active than in the thinner mice, whose UCP2 became even more active than before the tests started–apparently to help them burn off more calories.
UCP2 appears to work in concert with another gene, known as leptin, which tells the brain how full we are. It’s thought that the faulty action of leptin also plays a role in some cases of obesity.
The discovery of UCP2 holds out promise that a drug could be developed that mimics its action, which could help obese people burn off calories more efficiently. This would inevitably result in an increase in body temperature, however, so taking too much of it would bring on a fever. Still, in some people the health risks of being overweight might make it worthwhile.
But does this mean we’ll soon have a “magic pill” that will allow us to eat whatever we want and skip exercising entirely?
No. The fact is, controlling weight is complex and different in every person. Sure, there’s a genetic component–the new gene may also help explain why some people seem to have a pre-set weight that they can’t vary much no matter what they do. But there are also psychological components to weight control (many people eat more fat when they’re feeling under stress, for example), other physical components–and always, that balance between exercise and eating.
For most of us, no matter what the discoveries of the geneticists, it’s that balance that’s out of whack.
March, 1997. Resolved to exercise more and eat less…again.
