We all know people who can eat whatever they want and never put on an ounce (though oftentimes the pounds do sneak up on them as they age). Genetics clearly is a factor in how easily someone loses weight. Also, gender differences play a role. When men lose weight they tend to lose abdominal fat first, whereas women have a more difficult time losing abdominal fat. However, there are additional, more controllable contributors.
Amount of muscle mass
First, muscle mass is directly proportional to metabolism, and thus calories burned. People who have a large muscle mass burn more calories and can more easily lose weight when they control caloric intake than someone who has a low muscle mass. Therefore, if you want to optimize your weight loss success incorporate strength training into your routine in order to build muscle mass and increase overall metabolism. This also helps to ensure that any weight you do lose will be fat and not muscle. Keep in mind that your metabolic rate will still stay high even once you’ve lost weight.
Different starting points
Secondly, people who have more weight to lose initially experience rapid weight loss when they decrease their caloric intake and increase physical activity. This is because their baseline is often a very high calorie diet. For example, if someone who weighs 250 pounds and normally eats 3000 calories per day, if he/she cuts back to 2200 calories per day and expends 300 more calories per day with exercise, he/she can easily lose two pounds in one week. On the other hand, if someone who weighs 125 pounds and normally eats 2200 calories per day cuts back to 2000 calories per day and expends 200 more calories per day with exercise, he/she will only lose about .75 pound in a week. This reality partly explains why contestants on the Biggest Loser can drop exorbitant amounts of weight each week.
Change in behavior
Finally, behavioral factors cannot be ignored. Some people are more successful at losing weight because they are better able to adhere to a lower-calorie diet and regularly engage in physical activity. In the end, it comes down to calories. In order to lose weight you have to expend more calories than you consume. It takes about a 3500 calorie deficit to lose one pound. Start keeping track of your intake and approximate your expenditure. You should start to see the pounds come off, though some people may lose more quickly than others. If you continue to cut calories and increase physical activity and you still don’t notice any weight loss consider checking in with your doctor. It’s possible that you could have a medical condition that’s preventing you from being able to lose weight.
Natalie Digate Muth, MD, MPH, RD, is a registered dietitian and recent graduate of the UNC School of Medicine. She is an ACE-certified Personal Trainer and Group Fitness Instructor, and holds additional certifications with the American College of Sports Medicine and the National Strength and Conditioning Association. She has made several appearances as a nutrition expert on CW's San Diego 6, been quoted as a fitness expert in the New York Times and other newspapers and is an ACE Master Trainer and award-winning author. She is currently a pediatrics intern at UCLA Mattel Children’s Hospital.