In a weight-loss contest, the morbidly obese have an advantage over those who are less portly because they can shed fat more quickly. This is why contests, such as “The Biggest Loser,” use weight-loss percentage to track progress rather than simply counting the lost pounds. Biophysics and a history of poor choices, oddly enough, give overweight people a greater opportunity to lose more weight more quickly than their slimmer counterparts.
Weight Loss Principles
People lose weight by decreasing the number of calories they eat and by increasing how many calories they burn by exercising. For every 3,500 calories you burn through activity and don't use for energy, you lose approximately 1 pound of fat. This means that creating a 1,000-calorie deficit each day results in a loss of 2 pounds per week.
More Sedentary Lifestyle
People who are obese tend to lead more sedentary lifestyles. A lack of physical activity seems to contribute to the risk of gaining weight, but it also contributes to a continued disinclination to be physically active. Generally, those who are obese tend to be inactive, so even a modest amount of exercise can represent a significant increase in activity and calorie burn.
Overweight people have greater mass, so they have biophysics in their favor when they exercise. The more someone weighs, the more calories he burns in activity. They have greater mass to propel, so it requires more energy to move that mass. A 150-pound person burns about 236 calories walking at 3 mph for 60 minutes; it would take him more than two weeks of daily hour-long walks to burn off 1 pound. A 250-pound person burns 393 calories in 60 minutes of walking at 3 mph, so he would burn off 1.7 pounds in the same time period. Of course, he would have worked harder at it, because he had more weight to move around.
Higher Basal Metabolism
Your basal metabolic rate, or BMR, is the number of calories you burn maintaining the operations of your body over the course of the day while at rest. Even when you are inactive, your body burns calories running your brain, lungs, heart, kidneys and other organs, and it also uses energy repairing and replacing cells and tissues. Bigger bodies have higher maintenance costs. The more you weigh the more calories you burn, even when you do nothing. A 5-foot, 8-inch tall, 40-year-old female who weighs 150 pounds has a BMR of 1,433 calories, estimates the calorie calculator on ExRx.net. Her 250-pound counterpart has a BMR of 1,863 calories, a 430-calorie difference. If they were both placed on the same calorie-restricted diet, the heavier woman would have a greater calorie deficit between what she ate and what she needed to maintain her weight. The heavier woman could lose as much as 1 pound more every eight days because of her greater metabolism.
More Bad Eating Habits
Overweight people have been participating in an excess of calories, probably for years. In terms of bad eating habits and trying to identify high-calorie foods to eliminate from their diets, overweight people have what can be thought of as a target-rich environment. They likely have certain energy-dense foods that contribute disproportionately to their calorie intake. For example, the overweight person who drinks a liter of soda a day can drop 400 to 500 calories a day simply by replacing full-sugar soda with tea, water or diet-soda. Those who have leaner habits have to look more carefully to identify nutritionally-light, high-calorie foods to eliminate from their diets. In a similar vein, the obese person who is accustomed to eating 3,000 calories a day will drop weight a lot faster when he drops down to a more normal calorie intake of 2,000 calories per day than the thinner person who is already eating barely more than 2,000 calories a day.