For the most part, weight loss boils down to achieving a negative energy balance -- burning more calories than you put in your body. However, losing weight isn't always that simple or predictable. The body uses that energy obtained from food for three things: metabolism, digesting food and physical activity. Multiple factors affect these three areas, making weight loss less predictable than you might think.
Expectations
Matching your expectations with scientifically proven nutritional guidelines is important to your long-term success. Multiple weight loss advertisements and programs market "ideal" results inconsistent with realistic expectations. To mask this, these same companies generally include in the small print: "not typical results." The American College of Sports Medicine recommends a healthy goal of 1 to 2 lbs. of weight loss per week, which equates to a 3,500- to 7,000-calorie deficit each week.
Calorie Estimates
With realistic expectations in line, take a look at your daily calorie estimates. In his book "Fit and Well," researcher Thomas D. Fahey indicates that Americans significantly underestimate portion sizes by up to 25 percent and their daily intake by nearly 600 calories. This equates to a mathematical error that would equal 1 lb. per week, which could easily derail even the most committed dieter. Use one of the many free and accurate online calorie counters to help you keep track of your food intake.
Genetics
Genes may limit our ability to lose weight. In a related study, Gregory S. Barsh estimates that genetics contribute up to 90 percent of weight control in an article in "Nature." The high range reflects what scientist call the set point theory -- a belief that regardless of attempts to lose weight, the body will remain or go back to a genetically predetermined weight range. Other researchers, such as Fahey, agree that genetics have a strong influence on weight but contributes closer to 20 to 40 percent, citing lifestyle and its interaction with genes as being the major contributor to weight management.
Resting Metabolic Rate
Resting metabolism -- the base level of energy production needed for survival -- is thought to contribute to 55 to 75 percent of all daily energy burned. Things like physical activity, increasing muscle mass and eating increase that metabolic rate. However, severe dieting may have an opposite effect, sending the body into a "survival" mode of sorts, and lowering the metabolic rate according to George Brooks in "Exercise Physiology: Human Bioenergetics and Its Applications." To take advantage of the increased metabolism from eating, eat five to six small meals a day instead of the traditional three large meals.
Conditions
Nutritionist Carol Ward-Bredbenner states in "Wardlaw's Perspectives in Nutrition" that hormonal abnormalities, hypothyroidism, genetics and tumors on the pituitary gland -- a pea size gland that helps control hormone production -- may be among several rare conditions that throw off the body's normal way of producing and using energy. All of which, ultimately, contribute to an inability to manage weight. If you suspect any of these rare conditions, consult your physician.
References
- "ACSM's Resource Manual for Guidelines for Exercise Testing and Prescription"; American College of Sports Medicine; 2006
- "Wardlaw's Perspectives in Nutrition"; Carol-Byrd Bredbenner, Gaile Moe; Donna Beshetoor; Jacqueline Berning; 2009
- "Exercise Physiology: Human Bioenergetics and Its Applications"; George Brooks, Thomas Fahey, Kenneth Baldwin; 2005
- "Fit and Well;" Thomas D. Fahey, Paul M. Insel, Walton T. Roth; 2009
- "Nature"; Genetics of Body Weight Regulation; Gregory S. Brash, I. Sadaf Farooqi, Stephen O'Rahilly; Apr. 6, 2000
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