Effective ways to lose weight — what does the evidence say?

January is the most popular month for ads on weight loss products and services. With so many enticing options for slimming down, choosing the one that will work the best can be daunting. Researchers at the University of Arizona reviewed evidence-based strategies for treating adult obesity to find the options with the most promise for success. Here are some highlights of what they found:


  • Most weight loss programs cut calories by diet alone or combine it with exercise. Current research suggests that weight loss depends more on restricting total calories than on changing the type of food or nutrients eaten (such as low carbohydrate or low fat diets).
  • The strongest predictor of losing weight and keeping it off is sticking to the weight loss plan. Regular contact with the program and social support can help you stay with it over time.

Physical activity

  • Evidence supports combining physical activity with cutting calories. A large amount of exercise is needed to lose weight without reducing calories, and combining more exercise with less food helps avoid the loss of lean body mass and lowered metabolic rate that occurs with dieting alone.
  • Exercise improves fitness even without significant weight loss. Percent of weight lost as fat and reducing abdominal fat is greater with exercise than diet.
  • During weight loss, aim for 150 to 420 minutes of moderate to vigorous activity a week. Regular exercise, about 200 to 400 minutes a week, is the best way to maintain weight loss.


  • The longer a person stays with a program, the longer it will work. Self monitoring diet and physical activity behaviors can help a person stay on board and lose weight. But over time, boredom overtakes the effectiveness of rewards, behavioral cues and reminders in making lifestyle changes.
  • Maintaining positive thoughts about self worth and body image and committing to lifestyle change can help with weight loss and prevent weight regain.

Weight loss drugs

  • Over-the-counter weight loss supplements claim to work in many ways such as decreasing appetite, increasing calories burned, reducing fat absorption and improving mood. But safety is a concern and evidence that these supplements work long term is weak.
  • Prescription weight loss drugs are more effective when combined with cutting calories, exercise and behavior change. Weight loss is modest, about 5% to 10% of body weight, and usually plateaus at 6 months.


  • The Roux-en-y-gastric bypass, which bypasses 95% of the stomach and part of the colon, is the most widely used surgery for the very obese person (about 100 pounds over ideal body weight, BMI over 40 or 35 with obesity-related health conditions). Most people lose 35%-40% of body weight, and are able to maintain it for at least 15 years. It may reverse type 2 diabetes.
  • Adjustable gastric banding puts a band around the upper stomach to reduce the size of the stomach and the amount of food eaten at one time. It can be done laparoscopically, is reversible and has fewer complications than gastric bypass surgery. Weight loss varies and is generally less than gastric bypass.


  • No matter the approach used, there is wide variation in weight loss and maintenance results, even with good compliance. This suggests that genes, as well as environment, play a role in a person’s response to treatment. Research on genes and weight loss is advancing, but not yet enough for weight loss programs to be individualized based on a person’s genes.

Bottom line: Regardless of the weight loss approach that’s right for you, lifestyle changes that include healthy food choices, portion control and regular physical activity are essential. For many obese adults, even a 5% to 10% weight loss can improve health. For guidance and ongoing support, speak with your doctor and experts in nutrition, exercise and behavior change.

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