Doing the Math

Leslie Beck is a registered dietician in Toronto who also writes a regular column entitled "Food For Thought" for the Globe and Mail.

There's nothing "health at every size"y about Ms. Beck. A large proportion of her articles deal with how to lose weight. Yes, she does stress eating healthy foods and does not tout fad diets, but her bottom-line message is that we are all better off losing weight. Weight loss is the holy grail.

I was somewhat intrigued, nevertheless, by one of her columns, "The New Weight-Loss Math", published in the G&M on February 22, in which she explains how the standard weight loss math--so beloved of so many weight-loss warriors--just doesn't work out as advertised:

According to U.S. researches, this ubiquitous weight-loss [NewMe here: in other words, cut 3,500 calories and you will automatically lose 1 pound] rule is overly simple and overly optimistic. And it can lead to unrealistic expectations about how quickly you can achieve a weight-loss goal.

The rule contends that cutting 200 calories a day from your diet would lead to a loss of 20 pounds over the course of a year and the weight loss should keep on going. But in reality that doesn’t happen. Weight loss slows and eventually comes to halt despite the drop in calorie intake.

This past weekend, at the American Association for the Advancement of Science’s annual meeting in Vancouver, an international team of researchers unveiled a new formula to better predict how people will lose weight on a diet.

The 3,500-calorie assumption doesn’t account for how metabolism changes during weight loss.

Your metabolism is the rate at which your body burns calories, and it’s largely determined by how much muscle you have, since muscle burns more calories at rest than body fat. Ultimately, it’s your metabolism that dictates how easily you will lose or gain weight.

As the body slims down, metabolism slows, causing it to burn fewer calories at rest. A smaller body also burns fewer calories during exercise. The net result: a sluggish rate of weight loss that can frustrate dieters and cause them to abandon their plan.

Now health-care professionals and researchers have a tool to more accurately predict a dieter’s expected weight loss over time, based on changes to metabolism. Having a more realistic sense of what to expect can help people stay motivated over the long term.

The new formula and accompanying web-based model were developed by researchers from the U.S. National Institutes of Health, the World Health Organization, Columbia University and Harvard School of Public Health,

The online tool – called the Body Weight Simulator – requires people to input their age, gender, body weight, height, activity level and weight goal (bwsimulator.niddk.nih.gov).

It then simulates what diet and exercise changes are required to reach the goal weight and what changes are necessary to maintain it over time.

Using this model, the researchers found that people’s bodies adapt slowly to dietary changes.

For example, the average overweight person needs to cut 100 calories from their current intake per day to lose 10 pounds over three years.

Half of the weight will be lost in one year and then you’ll reach a plateau, slowly losing the remainder by three years.

In contrast, for the same calorie reduction, the 3,500-calorie formula predicts you’ll lose 10 pounds in one year – and 30 pounds by three years.

I tried out the weight loss simulator myself and found that, given my inability to do heavy exercise, to lose weight I would have to starve. And to keep the weight off? I would have to starve slightly less. As it stands right now--and without doing a serious analysis of my daily caloric intake--I eat healthy foods in reasonable portions, ask myself if I am hungry before eating those few dried apricots, sometimes eat them anyway and sometimes desist, and am basically holding my weight steady. I really don't think that it is either healthy or feasible for me to feel constantly hungry for the rest of my life.

The only thing that I regret is the inability to do exercise that would help me increase my muscle mass. Worse yet, my orthopedic and thyroid adventures have "helped" me to lose further muscle mass. (Re)building muscle mass, I believe, would be a laudable goal--were it possible for me to do so. Indeed, I often wonder what my weight would be today if I weren't so limited in the physical activity that I can safely do. I suspect that I would weight slightly less, but that my body would never agree to be thin--unless I became anorexic and that is not in the cards.

Ms. Beck's article goes on to stress that you must soldier on, even when your weight loss stalls. She suggests the regular tactics, mainly insisting that you must be ultra-vigilant at all times with respect to every single bite you put in your mouth. It's the regular diet talk: what's considered disordered eating for an anorexic is to be applauded in a dieter.

In the meantime, as for me, I keep walking...