An estimated 45 million Americans go on a diet each year, spending roughly $4 to $5 billion a year on weight loss products. Considering the fact that about one third of Americans are overweight and another third are obese, attempts at dropping pounds are proving to be futile for many adults. Researchers who have studied the weight problem have found that stress and denial are just a few of the reasons dieters don't lose weight.
Stress
A 2010 study published by the "Journal of Neuroscience" find that yo-yo dieting, a habit of temporary weight loss, may change how the brain responds to stress, which can lead to overeating in response to worry, fear and anxiety. In the study, University of Pennsylvania researchers put mice on a low-calorie diet for three weeks, causing them to lose between 10 to 15 percent of their body weight, results similar to those found in human studies. The researchers then put the mice in stressful situations and monitored their fat intake. The mice that were previously on a restricted-calorie diet ate more high-fat foods compared to ordinary mice. The researchers theorize that long-term dieting and fluctuating weight can change your brain chemistry and alter genes responsible for regulating stress and eating.
Overeating
It's possible that you're underestimating your calorie intake. A 2006 study by researchers at Cornell University found that people who are overweight tend to underestimate how much they eat by twice as much as people who are normal weight. While previous studies found that overweight people tend to underestimate calorie intake by 40 percent, compared to average weight people who underestimate calorie intake by 20 percent, researchers from the 2006 study believe that it's the size of the meal, not the size of the person, that determines a person's calorie-counting accuracy. One reason researchers may have believed overweight people underestimate more is because they do tend to eat more.
Exercise
While directly following a vigorous workout the appetite tends to decrease, as soon as the body normalizes, appetite typically increases, which could negate weight loss efforts. Dr. James Fries, Stanford University professor of medicine, explains that if you burn 300 calories while exercising and snack on a 200-calorie food, you can lose weight. The person who eats a plate of pasta or a few cookies after exercise will likely take in a few hundred more calories than expended through working out and will put on pounds. Also, exercise does not burn as many calories as some people believe. A 125-lb. person will burn 270 calories after 30 minutes on an elliptical trainer. One scoop of ice cream can contain nearly that many calories.
Weightlifting
Healthy adults should do strength-training exercises at least twice a week. While weightlifting can tone muscles, prevent chronic illnesses and improve your physique, it can also sabotage your weight loss efforts. Weightlifting builds muscle mass. Since inch for inch muscle weighs more than fat, weightlifting can add pounds. The reason you shouldn't let that get in the way of your twice-a-week strength-training program is that while the scale might not budge, regular weightlifting can tone the fat on your arms, legs, face and buttocks, resulting in a slimmer physique.
References
- ScienceDaily: Yo-Yo Dieting Alters Genes Linked with Stress; Dec. 1, 2010
- Cornell University: ChronicleOnline: It's the Size of the Meal, Not the Size of the Person, That Determines How People Underestimate Calories; Susan Lang; Nov. 1, 2006
- Boston.com: Does Exercise Increase or Decrease Your Appetite?; Judy Foreman; Nov. 10, 2008
- Harvard Health Publication: Calories Burned in 30 Minutes for People of Three Different Weights; July 2004
- American College of Sports Medicine: Physical Activity Guidelines
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