Weight loss and gain

• BIOLOGY
• ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, muscles, musculoskeletal system, psychic-emotional system, stomach

DEFINITION: Weight loss occurs when less energy is ingested than expended, while weight gain occurs when more energy is ingested than expended; both conditions may exist due to changes in diet or physical activity.

Process and Effects

Whether a person gains or loses weight is dependent on the balance of energy expended versus energy ingested. Thus, weight is determined by how many kilocalories are in the foods eaten and how many kilocalories of energy are expended. Normal day-to-day fluctuations in weight are typically minor changes attributed to shifts in body fluid and are not related to energy balance (input versus output). Input kilocalories refer to those from fat, protein, carbohydrates, and alcohol. Although alcohol is not considered an energy-yielding nutrient, it provides 7 kilocalories per gram. Output kilocalories are used to maintain the body’s basal metabolism; digest process food; fuel muscular activity for physical exercise; breathe; maintain body temperature; and help the body adapt to environmental changes. When energy intake exceeds output, a person gains weight. When energy output exceeds intake, a person loses weight.

Body weight is determined by the amounts of body fat, water, lean tissue (muscle), and bones. Ideally, what people want to lose when dieting is body fat, not lean tissue. It takes approximately 3,500 excess kilocalories to store a pound of body fat, whereas approximately 2,000 to 2,500 kilocalories are required to gain one pound of lean tissue. Any excess food kilocalories—whether from fat, carbohydrates, protein, or alcohol—can be converted into body fat. There is no limit to body fat stores. During periods of caloric deficit (meaning that input is less than output), a person will lose weight. A deficit of 500 kilocalories per day translates into a loss of about one pound per week. During a deficit or fasting, the body draws on stores to provide energy.

Caution should be used before an individual undergoes either a weight loss or a weight gain plan. Very low kilocalorie diets and meal skipping are not wise. These diets promote water and muscle loss, not steady body fat loss. A reduction in kilocalories of 250 to 1,000 per day will promote safe, effective fat loss without medical hazards. By consuming a balanced diet that contains all food groups in moderate portions, exercising, and modifying poor dietary behaviors (such as snacking while watching television), an individual can achieve lasting weight loss. Nutrient-dense foods—those that are low in kilocalories yet still contain ample amounts of vitamins, minerals, and fiber—should be chosen. Understanding the kilocaloric content of foods is not always necessary if a person uses exchange lists (diabetic exchanges), which are portion-controlled groupings of foods with similar energy contents that can be used to form an adequate diet. Exercise is important because it not only tones the body but also allows for more energy expenditure. Research has shown that regular exercise speeds up the basal metabolic rate (BMR), which also helps control weight. A person's BMR measures their daily energy expenditure at absolute rest. One's BMR is calculated based on age, gender, height, and weight. Multiplying a person's BMR by a factor based on their daily physical activity level gives an estimate of total daily calorie burn.

Most individuals seeking weight gain want to gain muscle, not body fat. Weight gain of this type can be accomplished by physical conditioning and a higher-calorie diet. The amount of muscle gained is under hormonal control. In healthy individuals, an excess of 1,000 kilocalories per day is sufficient to add two pounds per week. This excess must be accompanied by exercise training, however, or only body fat deposits will increase.

Healthy individuals desiring weight gain need to exercise and ingest more kilocalories in order to increase muscle size. Consuming more kilocalories can be problematic, especially for athletes. These individuals must take time to eat, perhaps five to six times per day. These individuals should eat more calorically dense foods—the exact foods avoided during weight loss. Emphasis should still be placed on nutrient-wise choices, not simply empty kilocalories. If someone is underweight, increasing fat in the diet is not considered a major heart disease risk because the fat will prevent muscle wastage.

Complications and Disorders

Not all weight gain or loss is voluntary. Weight changes can be warning signs or consequences of disease. Several diseases are frequently accompanied by severe weight loss and wasting, such as acquired immunodeficiency syndrome (AIDS), cancer, colitis, chronic obstructive pulmonary diseases (such as emphysema), cystic fibrosis, and kidney diseases. Wasting is characterized by decreased muscle mass and depleted fat stores. This is a result of inadequacies in both kilocalories and nutrient intake. A lack of appetite, or decreased desire to ear, termed anorexia, could be a consequence of disease, drug therapy, or both, complicating a person’s desire to eat. Severe weight loss is compounded by other nutrient losses caused by diarrhea, loss of blood, or drug interactions. Individuals with AIDS can experience extreme weight loss, perhaps losing up to 34 percent of ideal body weight, though in the twenty-first century, extensive progress has been made in fighting both AIDS and its side effects.

Thus, with illness, a vicious cycle occurs: A lack of adequate food energy promotes the risk of infection; infections require more food energy for healing, further depleting energy reserves; and patients lose more weight, placing them at greater risk for subsequent infections. Extreme weight loss makes patients with AIDS prone to other infections, which subsequently compromise weight status because more kilocalories are needed to combat these infections. Similarly, patients with cancer, colitis, and chronic obstructive pulmonary disease who experience weight loss become nutritionally compromised, placing them at risk for infections and delayed wound healing. Extra kilocalories are required to support the labored breathing accompanying chronic obstructive pulmonary disease. People with emphysema, a type of this disease, are often too weak to ingest enough food to prevent weight loss. Diseases of the gastrointestinal tract magnify poor nutritional status because energy-yielding nutrients cannot be absorbed.

Weight loss is also a symptom of cystic fibrosis. Cystic fibrosis is a genetic disorder that affects the pancreas and lungs. Individuals with this disease become malnourished because the normal release of pancreatic digestive enzyme secretions is impaired and because of high nutritional needs to combat lung infections. In an effort to clear congested lungs, individuals with severe cystic fibrosis may cough so forcefully that they frequently vomit any food substances that they were able to consume.

Treatment for illness-related weight loss is complex. Individuals do not always want to eat, for both physical and psychological reasons. More frequent meals, higher fat intakes, and even special nutritional supplements are required. In severe cases, intravenous solutions, tube feedings, and hyperalimentation (feeding higher-than-normal amounts of nutrients through tube feeding or veins) may be implemented. The cannabinoids in medical marijuana have also proven successful in increasing the appetites of those suffering from illness. Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the two most studied components and have proved invaluable in allowing those suffering from weight loss due to illness to increase their kilocalorie intake.

Sudden, dramatic weight loss could be a sign of dehydration. Athletes exercising during hot weather must pay attention to weight loss after practice and replenish fluids immediately. Rapid weight loss in teenagers, especially girls, may be attributable to eating disorders such as anorexia nervosa (self-induced starvation) and bulimia (periods of binge eating followed by intentional vomiting, or purging). Being underweight increases the risk of infections and infertility in women. On the other hand, binge eating disorder can lead to significant weight gain. Binge eating disorder is the most common eating disorder in the United States. Binge eating disorder is characterized by recurrent episodes of binge eating and feeling out of control of one's intake during these episodes. Binge eating involves eating much more rapidly than usual, eating until uncomfortably full, eating large amounts of food when not feeling physically hungry, or feeling shame or guilt afterward.

Patterns of weight gain or loss are important indicators of childhood growth. Rapid changes may signal illnesses or psychological problems that have manifested themselves as overeating or undereating. Tracking weight gain during pregnancy is also important. Gaining weight too rapidly may be a sign of fluid imbalance, forewarning pregnancy complications. Weight gain may precipitate insulin-dependent (type 2) diabetes mellitus. The location of excess weight on the body is also important. Individuals who gain excess weight in the waist area are considered to be at risk for hypertension, type 2 diabetes, and other disorders. Women are advised to gain no more than thirty-five pounds during pregnancy.

Perspective and Prospects

While the principle of weight loss and weight gain are simple, they can be difficult to achieve because they must be sustained over the long term. It is estimated that one-fifth to one-third of the adult population in the United States is “on a diet” at any given time. Weight management is a long-term endeavor resulting from myriad short-term decisions. Success comes with setting and achieving realistic goals. Family or group support, positive and tolerant attitudes, regular meals representative of all food groups, and behavioral modification will sustain a healthy weight. Twenty to thirty minutes of exercising the large muscle groups every other day can prove a modest, effective way to burn fat and increase one’s metabolic rate. It also produces more lean muscle tissue, a goal for both dieters and gainers.

Whether weight gain or loss is the goal, healthful eating habits require one to make wise choices and understand that weight control is a lifestyle, not a quick fix. Individuals experiencing a weight gain or loss who are not voluntarily altering exercise or food intake should have a thorough physical examination to determine the root cause. In June 2013, the American Medical Association voted to classify obesity as a disease. The decision spurned a nationwide conversation about obesity treatment and prevention. In addition, it led some members of the United States Congress to consider expanding Medicare coverage to include weight-loss drugs and weight-reduction treatments. As the twenty-first century progressed, the obesity industry expanded rapidly. Bariatric surgery and its variations became highly sought-after medical procedures, with patients often going through the process on reality television. In the 2020s, it was observed that treatments for type 2 diabetes, such as semaglutide and tirzepatide, also caused patients to lose a large percentage of their body weight. This led doctors to prescribe these medications for weight loss as well.

Bibliography

Barasi, Mary E. Human Nutrition: A Health Perspective. 2nd ed., Oxford UP, 2003.

Brownell, Kelly D. The LEARN Program for Weight Management. 10th ed., American Health, 2004.

“Cannabis and Cancer.” American Cancer Society, 2024, www.cancer.org/cancer/managing-cancer/treatment-types/complementary-and-integrative-medicine/marijuana-and-cancer.html. Accessed 15 Nov. 2024.

Gilchrist, Karen. “Obesity Drugs to Be Worth $200 Billion in Next 10 Years, Barclays Says.” CNBC, 19 July 2023, www.cnbc.com/2023/04/28/obesity-drugs-to-be-worth-200-billion-in-next-10-years-barclays-says.html. Accessed 15 Nov. 2024.

"Healthy Living and Weight." Nutrition.gov, USDA, www.nutrition.gov/topics/healthy-living-and-weight. Accessed 15 Nov. 2024.

Pollack, Andrew. "A.M.A. Recognizes Obesity as a Disease." The New York Times, 18 June 2013, www.nytimes.com/2013/06/19/business/ama-recognizes-obesity-as-a-disease.html. Accessed 15 Nov. 2024.

"Prescription Weight-Loss Drugs." Mayo Clinic, Mayo Foundation for Medical Education and Research, 29 Oct. 2022, www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/weight-loss-drugs/art-20044832. Accessed 15 Nov. 2024.

Rolfes, Sharon Rady, Kathryn Pinna, and Eleanor Noss Whitney. Understanding Normal and Clinical Nutrition. 12th ed., Cengage Learning, 2020.

Stransky, Fred W., and R. Todd Haight. The Good News about Nutrition, Exercise, and Weight Control. Momentum, 2001.

Summerfield, Liane. Nutrition, Exercise, and Behavior: An Integrated Approach to Weight Management. Wadsworth/Thomson Learning, 2000.

Smith, Ann N., et al. Contemporary Nutrition. 12th ed., McGraw-Hill Education, 2021.

"Weight Loss Basics." Mayo Clinic, Mayo Foundation for Medical Education and Research, 1 Nov. 2023, www.mayoclinic.org/healthy-lifestyle/weight-loss/basics/weightloss-basics/hlv-20049483. Accessed 15 Nov. 2024.

"Weight Loss: Gain Control of Emotional Eating." Mayo Clinic, Mayo Foundation for Medical Education and Research, 2 Dec. 2022, www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/weight-loss/art-20047342. Accessed 15 Nov. 2024.