MYTHBUSTERS: The Nutrition Edition

How many calories are in a pound of fat?

‘A pound of fat is 3500 calories.’

This is absolutely critical according to the conventional wisdom because most weight loss programs are based on the oft-cited notion of creating a “calorie deficit.” We need to create a deficit of 500 calories a day and we will lose one pound in a week, is the common advice.

The reality? One pound of fat is NOT 3500 calories.

There are three assumptions we need to look at when determining how many calories are in a pound of fat:

1. There are 454 grams in a pound of fat.

2. There are 9 calories in a gram of fat.

3. Human fat is actually about 87% fat (much of the remainder being water).

Here’s a simple calculation: 454 x 9 = 4,086 calories. So a pound of fat is not 3500 calories!

If we factor in item number three, 87% of 4,086 is 3,555 calories, still not 3500 calories!

To make matters more difficult, nine calories per gram of fat is an estimate: a closer approximation yields 9.3 calories per gram. Add this adjustment to the 3,555, and now we’re staring at a whopping total of 3673 calories.

Balancing caloric intake is the basis for the majority of weight loss programs. It also may be why the majority of weight loss programs are doomed to fail. A 2007 review from Tufts University looked at all of the relevant diet trials in the scientific journals since 1980.

“Prescribing low-calorie diets for obese and overweight patients,” noted Gary Taubes, author of Why We Get Fat, “leads, at best, to ‘modest weight losses’ that are ... temporary.”

“After a year,” wrote Taubes, “much of what was lost has been regained,” referring to the 2007 study.

Think about all of the people who add 30 pounds of fat from the graduation of college into the third decade of life. How many calories a day do we need to overeat by to gain 30 pounds in a little over a decade? Twenty-five calories!

“Weight management is all about balance,” claims the Centers for Disease Control and Prevention (CDC), “balancing the number of calories you consume with the number of calories your body uses or ‘burns off.’”

This idea is so pervasive that it may very well be the reason why we have an obesity epidemic and we can’t seem to do anything about it: consciously balancing calories consumed and expended is a physical impossibility.

Besting a 25-calorie deficit/surplus is to balance intake to expenditure by an accuracy to within 1% - on a 2500 calorie diet - “an exactness that is equaled by few mechanical devices and almost no biological process,” Eugene DuBois, the leading authority on nutrition and metabolism, noted more than 70 years ago.

“Such adjustment would not be possible without a specific mechanism that operates it; hence we must assume the existence in the body of a homeostatic body weight regulatory mechanism,” wrote Hugo Rony in 1940, an endocrinologist and director of of the Endocrinology Clinic at the Northwestern University Medical School.

To fatally complicate matters in this world of ‘calories-in/calories-out,’ the Food and Drug Administration (FDA) allows food manufacturers to “round down” the number of calories in foods.

For example, 104 calories of cookies will be listed as 100 calories on the Nutrition Facts label of some of our favorite 100-Calorie Packs, that, according to some authorities, aren't a problem for human obesity, so long as we count calories.

If we were to eat all of the servings according to the recommendations of the 1992 Food Pyramid, for example, and each serving were rounded down by four calories, as allowed by the FDA, we would be consuming 60-104 calories that would be unaccounted for.

We can have supposed control over our calorie-counting, assume we know that there are 3500 calories in a pound of body fat, and yet, we can pack on 100 pounds in a decade according to this arithmetic.

The good news is that it’s people like DuBois and Rony who had it right: obesity is a disorder of excess fat accumulation, not energy balance. We’re biological creatures, not thermodynamic garbage cans.

Perhaps we don’t get fat because we overeat. We overeat because our fat tissue is accumulating excess fat. There’s a profound difference: the former is blamed on behavior, the latter on the biology of the human body.

In upcoming posts I’ll propose that the rapid increase in the nationwide prevalence of obesity is not from a sudden epidemic of weak will, rather a problem borne of physiologic abnormality. We’ll delve a little deeper into why we get fat, how we can remedy it, and how the notion of practicing energy balance is meaningless in the prevention of obesity.

You shouldn’t be obsessing over how many calories are in that pumpkin pie and ice cream on Thursday. Eating these foods can, and will, contribute to fat accumulation over the holidays for some, but not for the reasons so many of us believe.

Bob Kaplan holds advance degrees in exercise physiology and business, an undergraduate degree in nutrition, is a nationally certified personal trainer, and owns four Get In Shape For Women locations in Bedford, Wellesley, Westford, and Winchester.

For more information about Kaplan's services at Get in Shape For Women in Winchester, please call 781-729-8100 or visit at 564 Main Street, Winchester, MA  01890, or online at www.getinshapeforwomen.com for a free week trial.