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JAMA Internal Medicine Patient Page
July 6, 2021

I Want to Lose Weight: Which Diet Is Best?

Author Affiliations
  • 1Department of Internal Medicine, University of Michigan, Ann Arbor
  • 2Division of General Internal Medicine, University of Utah, Salt Lake City
JAMA Intern Med. 2021;181(9):1268. doi:10.1001/jamainternmed.2021.3342

What Is a Healthy Weight?

To determine if your weight is in a healthy range, it is best to use body mass index (BMI), which takes into account both your height and weight. You can use an online calculator to determine your BMI (https://www.cdc.gov/healthyweight/assessing/bmi/). In general, a BMI greater than 25 is considered overweight, and a BMI greater than 30 qualifies as obese.

Overweight and obesity are associated with a higher risk of health conditions, such as high blood pressure, diabetes, heart disease, stroke, osteoarthritis, and some types of cancers. Even modest weight loss of 5% to 10% of your body weight can reduce your risk of many of these chronic diseases and improve quality of life.

How Does Diet Affect Weight Loss?

A person’s weight is associated with a combination of eating habits, access to healthy foods, physical activity, and genetics. The most fundamental factors in losing weight are the number of calories you eat and the number of calories you burn by exercising. Calories are the units used to measure energy in food and drink. For most people, steady weight loss ( ~ 1 lb/mo) can be achieved if you reduce your intake to 1200 to 1500 calories per day for women and 1500 to 1800 calories per day for men. Multiple easy-to-use calorie counters are available online.

What Should I Know About Specialty Diets for Weight Loss?

A Mediterranean-style diet is associated with a reduced risk of heart disease in addition to modest weight loss. It is primarily plant-based and emphasizes fruits, vegetables, beans, nuts, whole grains, and healthy fats such as olive oil and seafood while avoiding added sugars and highly processed foods.

Low-fat diets (Ornish) and low-carbohydrate diets (Atkins, South Beach, ketogenic, etc) can both be effective ways to reduce total calories. They lead to similar weight loss. Vegetarian or vegan diets, which include few or no animal products, have also been associated with modest weight loss and reduced risk of heart disease and diabetes.

Some diets involve continuous fasting for 1 day or more (intermittent fasting). Other diets recommend restricting eating to certain hours of the day (time-restricted eating). Both approaches led to weight loss that was similar to that from eating a balanced, low-calorie diet.1 Any diet that strictly limits the variety of foods you can eat (ketogenic, vegan, etc) may place you at risk for nutritional deficiencies. Care must be taken to get adequate nutrients such as iron and B vitamins.

Which Diet Should I Choose to Lose Weight?

It is important to choose a diet that is healthy and that you can stick to. For most people, eating a balanced low-calorie diet is a safe and proven approach to losing weight that can be followed life-long. Combined with 150 minutes of moderate-intensity physical activity per week, this approach to eating can lead to many other health benefits as well. Set specific diet-related and exercise-related goals and work to achieve them step by step. It is normal to slip back into old eating habits occasionally; the important thing is to return to your weight loss plan after these episodes.

The diet you choose should be based on your lifestyle and any existing medical conditions. Ask your doctor or a dietician about resources to learn more about weight loss and healthy eating.

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Section Editor: Michael Incze, MD, MSEd.
The JAMA Internal Medicine Patient Page is a public service of JAMA Internal Medicine. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA Internal Medicine suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, email reprints@jamanetwork.com.
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Article Information

Published Online: July 6, 2021. doi:10.1001/jamainternmed.2021.3342

Conflict of Interest Disclosures: None reported.

Lowe  DA, Wu  N, Rohdin-Bibby  L,  et al.  Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity: the TREAT randomized clinical trial.   JAMA Intern Med. 2020;180(11):1491-1499. doi:10.1001/jamainternmed.2020.4153PubMedGoogle ScholarCrossref
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