Weight loss is defined as any sustained effort to lose excess body mass—most often fatty tissue—however, athletes and others might desire to lose fluid or muscle weight for athletic or other purposes.
Body mass index (BMI) is described as a measure of body fat that is the ratio of the weight of the body in kilograms to the square of its height in meters. Overweight is defined as having a body mass index (BMI) of 25.0–29.9; obesity is defined as having a BMI of 30 or greater.
Weight gain, overweight, and obesity are caused by an imbalance that occurs as a result of a number of factors. The key reasons are:
Obesity is a leading indicator of chronic disease and is directly linked to the most prevalent cause of death in men and women—heart disease. In the United States, the occurrence of obesity has doubled in the past 20 years; more than one-third of all adults are now obese. In addition, the occurrence of overweight and obesity among children and adolescents has risen markedly. About 17% of children and adolescents are obese.
Obesity and excess body fat are significant indicators of the leading causes of chronic disease and premature death including heart disease, type 2 diabetes, stroke, hypertension, dyslipidemia (high cholesterol), gallbladder disease, respiratory disease, gout, osteoporosis, and certain cancers (e.g., colorectal and breast cancer).
The key to maintaining a healthy weight at any age or height is in balancing the total calories consumed from food and beverages with those calories expended by physical activity and exercise. Most Americans consume calories well in excess of those they burn by activity and exercise. According to the U.S. Department of Agriculture (USDA), the average calories consumed by Americans increased from 2,234 calories per day in 1970 to 2,757 calories per day in 2003; the number was estimated to be at least 2,640 for men and 1,785 for women in the agency's 2010 dietary guidelines. This 500-calorie-per-day increase accounts in large part for the rise in overweight and obesity rates seen in Americans over the same period. Since 2010, Americans have been eating slightly fewer calories, but not necessarily healthy calories. For example, the 2015 guidelines report average intakes of sodium in Americans as a percentage of calories. Among adult men, sodium intake was reported at 4,240 mg per day compared with the average recommended intake of 3,440 per day.
The portion size for the average American diet has grown notably larger in recent decades; restaurants are now serving larger portions than were customary 20 or even 10 years ago. Packets of snack foods in vending machines and in convenience locations are frequently in sizes larger than single serving, and economy meals in fast food restaurants offer portion increases at inexpensive price points. Prepackaging, shipping, and long-term storage of foods for distribution in the global market have driven down the costs of many foods and, therefore, the quality, creating a market saturated with cheaply produced foods high in saturated and trans fats and low in nutrients. Studies indicate that portion size is directly linked to the amount of food a person will consume in a meal and that consistently reducing portion size is an effective measure for weight loss.
Access to nutritious foods that are low in saturated and trans fats is more limited because these foods have grown increasingly more expensive than less healthy choices and are not distributed as widely. Historically, foods higher in fats and sugars were the more expensive choice, but globalization has changed this. Studies reveal the manufacture and global distribution of low-cost, high-fat, and high-sugar-content foods has made these foods more easily accessible than healthier choices for all social classes, as well as every age group and gender. In this way, obesity and weight-related illnesses are on the rise throughout the world, even in developing countries.
People seeking to extend health and deter aging and illness should incorporate healthy nutrition and regular exercise into their lives as much as possible. To that end, including fresh fruits and vegetables, whole grains, lean meats, and fat-free or reduced-fat dairy options are the dietary suggestions for optimum health in adults, children, and adolescents. In addition, 2015 dietary guidelines recommend cutting salt and added sugars.
Many regimens exist for losing weight, but the most consistently healthy programs, and the most consistently successful over the long term, mix reducing calories from fat and complex carbohydrates along with a program of regular, moderate exercise of 30 or more minutes per day, several days per week. Incorporating a healthy diet with moderate-to-intense exercise on a regular basis is enough to bring the body into balance and lower the risk of chronic disease and many causes of early death. A good, fat burning exercise is one that elevates heart rate. A moderate activity such as brisk walking for an hour can burn approximately 370 calories in a 154-pound individual. Walking at a regular pace (3.5 mph) can burn 280 calories for the same time period, and jogging/running (5 mph) can burn 590 calories.
Those weight loss programs found to be the most successful over the long term and which bring individuals the healthiest overall benefits are those that:
If overweight or obesity is a concern, it is important to have regular health checkups with a doctor, particularly if there is a family history of health conditions for which obesity is a risk factor. If overweight or obese, individuals need to be checked for heart disease and type 2 diabetes before beginning any exercise program. Children and adolescents with these conditions should also be checked by a physician, as health-related conditions associated with overweight are on the rise in the young.
Weight that is lost gradually is healthier for the body than weight lost suddenly and is more likely to be kept off over the long term. Research consistently reveals that weight-loss programs consisting of taking diuretics or other over-the-counter drugs or supplements by pill, drink, or shakes are not the most healthful options and should not be considered without the advice of a doctor. Relying solely on such programs for weight loss seldom results in consistent benefits and is not the best way to improve health during weight loss, maintain a healthy weight, or reduce weight for the purpose of preventing disease.
New diet strategies and programs regularly appear on the market, but few have ever been shown to be safe and effective for long-term weight loss. Likewise, it is better to rely on natural, unprocessed foods, such as fresh fruits and vegetables, than on processed diet foods. For example, a 2016 study showed that aspartame, an artificial sweetener in many diet drinks, can actually interfere with enzymes that break down fat and make weight loss more difficult.
A cool-down period is advised after aerobic exercise to gradually return the body to its resting heart rate. Stretching the muscles after exercise is advised to help with the release of lactic acid build-up in the muscles and to reduce any soreness in the days that follow. Stretching after the muscles have warmed also helps the body with flexibility and agility, and reduces the possibility of injury during normal movement as well as during future exercise.
The combined effort of regular, near-daily exercise consisting of aerobic activity for 30 or more minutes along with eating a healthy, well-balanced diet consisting of fresh vegetables, fruits, whole grains, adequate protein portions, and vitamins and minerals to include iron; zinc; and vitamins A, E, B6, B12, and C has proven to be the best means of achieving healthy weight. A balanced diet and exercise also can help prevent illness and disease, both current and future. Eating well and exercising consistently at moderate levels also helps reduce stress hormones and helps individuals fight or recover from illness. Weight-loss programs that incorporate these health concepts and teach individuals how to maintain a healthy weight, as well as offer tips and support for achieving a healthy lifestyle, tend to be the most effective over time.
See also Body mass index ; Carbohydrates ; Calories ; Fat ; Fat burning ; Obesity ; Protein ; Walking .
Moyer, Meagan F., and Academy of Nutrition and Dietetics. Bits and Bytes: A Guide to Digitally Tracking Your Food, Fitness, and Health. Chicago: Academy of Nutrition and Dietetics, 2017.
Bucklin, Stephanie. “Why Aspartame May Prevent Weight Loss.” LiveScience.com . http://www.livescience.com/57065-why-aspartame-may-prevent-weight-loss.html (accessed February 24, 2017).
Centers for Disease Control and Prevention. “Overweight and Obesity: Adult Obesity Facts.” U.S. Department of Health & Human Services. https://www.cdc.gov/obesity/data/adult.html (accessed February 24, 2017).
Coleman, Erin. “The Average Calorie Intake by a Human Per Day Versus the Recommendation.” SFGate.com . http://healthyeating.sfgate.com/average-calorieintake-human-per-day-versus-recommendation1867.html (accessed February 24, 2017).
“Dietary Guidelines for Americans 2015 to 2020.” Health.gov . https://health.gov/dietaryguidelines/2015/resources/2015-2020_Dietary_Guidelines.pdf (accessed February 24, 2017).
National Heart, Lung, and Blood Institute. “Assessing Your Weight and Health Risk.” National Institutes of Health, Department of Health & Human Services. http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm (accessed February 24, 2017).
Office on Women's Health. “Overweight, Obesity, and Weight Loss Fact Sheet.” U.S. Department of Health & Human Services. https://www.womenshealth.gov/publications/our-publications/fact-sheet/overweightweight-loss.html (accessed February 24, 2017).
Academy of Nutrition and Dietetics, 120 South Riverside Plaza, Suite 2000, Chicago, IL, 60606-6995, (800) 877-1600, http://www.eatright.org/ .
American College of Sports Medicine, 401 West Michigan St., Indianapolis, IN, 46202-3233, (317) 637-9200, Fax: (317) 634-7817, http://www.acsm.org/ .
Julie Jordan Avritt
Revised by Teresa G. Odle, BA, ELS