Can We Break the Biological Weight Barrier?

A 20-minute walk burns about 100 calories... There are 3,500 calories in a pound.

Scientists believe that each individual has a genetically determined weight variance of perhaps 30 pounds.

HEALTH Are you shocked by this statement, published in The New York Times? Does it seem that diet and exercise form a futile struggle to defy the brain's innate calorie counter? [1]

Is It All About the Food?

Americans have been gaining weight for decades. Two thirds are now overweight. In the 1960s, McDonald's was popular enough to have sold billions of burgers; home-cooked meals had plenty of butter; and American apple pie with refined white sugar and a glass of whole milk for desert was a tradition. So the argument that the progressive increase in obesity is due to fast food consumption is debatable. As we step back, other factors come into view.

A noticeable change in the digital age is that nearly everything is delivered to our seats. The library, the theater, concert, the mall, even grocery shopping are accessible from our desktop. With tremendous health risks, technology has bred an increasingly sedentary generation. This has spawned the emerging field of "inactivity physiology." [2]

Can We Burn All the Calories We Consume?

A basic weight loss principle is to burn more calories than we consume. For adults aged 18-64 the 2008 federal health guidelines state, "Adults should do 2 hours and 30 minutes a week of moderate-intensity, or 1 hour and 15 minutes (75 minutes) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic physical activity." [3]

A 20-minute walk burns about 100 calories. That's 300 calories per hour. Recommended daily calorie consumption is 2129 [4] (though many restaurant and processed food include as much or more in a single meal). Therefore, one would theoretically require 7 hours of moderate exercise to burn 2100 calories. There are 3,500 calories in a pound. [1] Unrealistic though it may be, it would seem that it would take around 12 hours of walking for the scale to register the loss of a pound. Are you wondering, "How could I ever burn more calories than I eat?"

Fortunately, there's something called the Basal Metabolic Rate [5]. It's the amount of calories your body burns through ordinary existence in a neutrally temperate environment. We burn moderate calories by sleeping! That's why dieters compare their weight at the same time each day — usually in the morning after evacuations.

The average woman's BMR is somewhere between 1100 and 1300 calories, and it increases with more muscle mass. Daily activities like gardening, washing the car or walking to the refrigerator burn another couple hundred calories to that. Vigorous workouts burn an additional 300 – 500 calories per hour. Add it up and you could be burning over 1600 calories a day. Individual BMR can be calculated based on height and weight. [6] Once you calculate your BMR, consume less calories to decrease weight. (The BMR for my age, weight and height is 1830, before exercising. —Ed)

Regular exercise also converts stored energy (fat) into muscle (which is heavier than fat). There are significant health benefits associated with cardiovascular exercise beyond weight loss. The processes involved with maintaining healthy weight are much more complex than just walking longer or, on the other extreme, dieting solely by BMR.

Genetics and Metabolic Syndrome

"There are physiological mechanisms that keep us from losing weight [1,7]," said Dr. Matthew W. Gilman, the director of the obesity prevention program at Harvard Medical School/Pilgrim Health Care. Based on over 15,000 clinical studies, the protein hormone leptin [8] apparently triggers the brain to adjust metabolism, maintaining a genetically established weight range within about 30 pounds. Eat less and the body conserves more. Increase consumption in an effort to go beyond that innate barrier and the metabolism rate speeds up to compensate. Like a rubber band, most who dramatically deviate from their genetic weight often return after the extreme caloric deprivations or fulsomeness. These are the battles with which we all contend to achieve the ideal Body Mass Index goals of 18.5 - 24.9 BMI.

A nine-year study of 48,500 U.S. men and 56,343 U.S. women has shown that the larger your waistline the higher the risk for mortality. [10]

Though exercise and healthy eating should not be diminished contributors to weight management, biological factors are at work. The American Heart Association has outlined characteristics of metabolic syndrome [9] (see sidebar), where several etiologies converge with genetics. For managing both long- and short-term health risks, lifestyle therapies are the first-line interventions to reduce the metabolic risk factors:

  • Weight loss to achieve a desirable weight (BMI less than 25 kg/m2)
  • Increased physical activity, with a goal of at least 30 minutes of moderate-intensity activity on most days of the week
  • Healthy eating habits that include reduced intake of saturated fat, trans fat and cholesterol

Paring Down the Risks

A nine-year study of 48,500 U.S. men and 56,343 U.S. women has shown that the larger your waistline the higher the risk for mortality — in fact, obesity doubles the risk. [10] An easy goal to remember is to keep your waist size less than half of your height. Just figure out your height in inches and divide by two. [11] With that in mind, one would need to be 6-foot 7-inches tall to justify waistline of 40 inches.

Because genetics play a significant role in our physique, there will continue to be variations in body shapes. It's not an excuse, but, for many, an obstacle with which to contend. Despite any biological weight barrier imposed by leptin and other physiological processes, we can still improve our health with sensible meals and exercise, even if we do not achieve the ideal BMI. Let's face it, 30 pounds is a relatively large range for variance. If we are at the high end of the scale, there is sufficient room to lose weight and keep it off. For morbidly obese persons, medical intervention can be discussed with the appropriate healthcare provider. Inaction is the worst response to obesity.

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Tags: dietician, endocrinology, fat, fitness, nutritionist, overweight, weight gain

  1. For the Overweight, Bad Advice by the SpoonfulThe New York Times, August 30, 2007
  2. Health Risks of Sitting. Stanford Center on Longevity, July 2010
  3. 2008 Physical Activity Guidelines for Americans. Department of Health and Human Services,
  4. Average calorie consumption,
  5. Basal metabolic rate. Wikipedia
  6. BMR Calculator.
  7. Leptin and the regulation of body weight in mammalsNature, Vol 395, October 22, 1998, (PDF)
  8. What is Liptin? Wellness Resources, Byron Richards, January 2009
  9. Metabolic Syndrome. American Heart Association,
  10. Waistline Clearly Linked to Mortality Risk. Wellness Resources, Byron Richards, August 2010
  11. Waist to Height Ratio – Is your Stomach Too Large? Wellness Resources, Byron Richards, June 2008