Weight management

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Weight management refers to behaviors, techniques, and physiological processes that contribute to a person's ability to attain and maintain a healthy weight.^[1][2] Most weight management techniques encompass long-term lifestyle strategies that promote healthy eating and daily physical activity.^[3] Moreover, weight management involves developing meaningful ways to track weight over time and to identify the ideal body weights for different individuals.^[4]

Weight management strategies most often focus on achieving healthy weights through slow but steady weight loss, followed by maintenance of an

The science behind weight management is complex, but one of the key concepts that governs weight management is Energy Balance.^[9] Energy Balance is the phrase used to describe the difference between the number of calories a person consumes and the number of calories that same person expends (a.k.a. burns) in a given time period.^[9] There are three possible scenarios when it comes to the energy balance equation:

• Calories consumed (food, drink) = Calories expended (basal metabolic rate, physical activity, thermogenic effect of food, acute illness)
  • Outcome: Weight remains unchanged
• Calories consumed > Calories expended
  • Also known as Positive Energy Balance
  • Outcome: Weight increases
• Calories consumed < Calories expended
  • Also known as Negative Energy Balance
  • Outcome: Weight decreases^[9]

The calories a person consumes come from food and drink intake.^[9] The calories a person expends comes from their basal metabolic rate and their daily physical activity.^[5] The human body is very good at maintaining a neutral energy balance, particularly with a diet composed of fruits, vegetables, and meats so that calories consumed do not substantially exceed calories expended in a given time period and vice versa.^[5] This energy balance is regulated by hormones like Leptin (suppresses), Ghrelin (stimulates), and Cholecystokinin (suppresses) which either suppress or stimulate appetite.^[5]

Diet

The quantity of food and drink consumed by an individual may play a role in weight management, as may the types of food and drink a person consumes.^[5][9][12] For example, intake of sweetened drinks such as sodas or juices can lead to increased energy intake that is not neutralized by a decrease in accompanying food intake.^[5] Increased portion sizes may also lead to increased energy intake.^[5]

Physical activity

Physical activity can be related to a person's professional activities, non-work related daily activities like walking or cycling, or it can be in the form of activities such as recreation or team sports. ^[5] The specific type of activity can be tailored to populations such as children, pregnant women, and elderly adults.^[5] Tailored activity to one's fitness level also encourages the body to heal properly and prevent any injuries as a result of exercise.^[16]

Physical inactivity leads to less energy expenditure and is a factor that impacts obesity rates in both children and adults.^[17] Physical inactivity has become a worldwide concern since inactivity also elevates the risk of heart disease.^[16] Regular physical activity can reduce the risk for noncommunicable diseases like diabetes, heart disease, and dyslipidemia (high cholesterol). ^[5]

Basal metabolic rate

Basal metabolic rate (BMR) is one of the main components of a person's daily energy expenditure. It is defined as the amount of energy that is expended during a given amount of time by a person at rest. This energy at rest is used to pump blood throughout the body, maintain proper brain function, break down toxins, and ensure other bodily functions. Technically speaking, BMR is the energy the body expends during the following specific conditions: immediately after waking up, while in a resting state, and after fasting for 12–14 hours. Sometimes the term Resting Metabolic (RMR) is used in place of BMR, but RMR is not solely measured under the previously listed stringent conditions and it is about 10% more than BMR.^[18]

The BMR is directly proportional to a person's

• BMR (Males) in Kcals/day = 66.47 + 13.75 (weight in kg) + 5.0 (height in cm) - 6.76 (age in years)
• BMR (Females) in Kcals/day = 655.1 + 9.56 (weight in kg) + 1.85 (height in cm) – 4.68 (age in years)[19]

The revised Harris-Benedict Equations are as follows:

• BMR (Males) in Kcals/day = 88.36 + 13.40 (weight in kg) + 4.8 (height in cm) – 5.68 (age in years)
• BMR (Females) in Kcals/day = 447.59 + 9.25 (weight in kg) + 3.10 (height in cm) – 4.33 (age in years)^[19]

The Mifflin St. Jeor Equation is as follows:

• BMR (Males) in Kcals/day = 9.99 (weight in kg) + 6.25 (height in cm) – 4.92 (age in years) + 5
• BMR (Females) in Kcals/day = 9.99 (weight in kg) + 6.25 (height in cm) – 4.92 (age in years) – 161^[19]

The Mifflin St. Jeor Equation has been found to be the most accurate predictor of BMR compared to BMR measured by direct and indirect calorimetry.^[19]

Body mass index

Body mass index (BMI) is a value used to get a general sense of a person's overall mass and is calculated using a person's height and weight. It is more often used than weight alone to determine if an individual is underweight, normal weight, overweight, or obese. The following two equations can used to calculate BMI depending on the units used for height (meters vs. inches) and weight (kilograms vs. pounds):^[5]

${\displaystyle \mathrm {BMI} ={\frac {{\text{weight}}_{\text{kg}}}{{{\text{height}}_{\text{m}}}^{2}}}}$

or

${\displaystyle \mathrm {BMI} ={\frac {{\text{weight}}_{\text{lbs}}}{{{\text{height}}_{\text{in}}}^{2}}}\times 703}$

Though BMI is often used to help assess for excess weight, it is not a perfect representation of a person's body fat percentage. For example, an individual can have a higher than normal BMI but a normal body fat percentage if they have higher than average muscle mass. This is because excess muscle contributes to a higher weight. Since BMI is not a perfect representation of a person's body fat percentage, other measurements like waist circumference are often used to better assess for unhealthy excess weight.

The following table shows how different ranges of BMIs are often categorized into underweight, normal weight, overweight, and obese:^[5]

On average, groups of people with "obese" BMIs may have a higher risk of developing illnesses like diabetes, hypertension, dyslipidemia (high cholesterol), liver disease, and some cancers. "Underweight" BMIs may indicate malnutrition or other health problems. However, BMI has limitations when used to describe individual health rather than describing populations of people. ^[5]

Complicating factors

Thermogenic effect of food

The

Certain medications can cause either weight loss or weight gain.[5] Such side effects are often listed for each medication and should be considered when attempting to manage a person's weight.^[5]

Metanalysis has shown that phentermine and topiramate, pramlintide, naltrexone, bupropion, and liraglutide have been shown to induce weight loss.^[21] Semaglutide is another anti-obesity drug that is also used for blood sugar control.^[22]

Diseases

Medical conditions associated with weight gain include hypothyroidism,^[23] Cushing's syndrome, Polycystic Ovary Syndrome (PCOS), and congestive heart failure.^[5][24] Medical conditions such as cancer, gastrointestinal illness, psychiatric disorders, infections, endocrine disorders, and neurologic disorders may lead to weight loss.^[5]

Commonly associated with weight gain

Polycystic ovary syndrome (PCOS), which is characterized by insulin resistance and hyperandrogenism, is a common condition that has been linked to obesity.^[25] A combination of genetics, lifestyle, and environment appear to contribute to the hormonal changes responsible for weight gain and obesity seen in individuals with PCOS.^[25]There appears to be a bidirectional relationship between obesity and PCOS, whereby PCOS increases the risk of obesity and similarly, obesity has been found to exacerbate PCOS hormonal differences and clinical symptoms.^{[25] [26]} Obesity has been linked with pancreatic β-cell dysfunction and insulin resistance.^[27] In diabetes, impaired β-islet cells are responsible for the lack of blood glucose control.^[27] Individuals with a higher body mass index concerning for obesity may have increased levels of hormones, proinflammatory markers, and glycerol, which can contribute to insulin resistance.^[27] The combined effects of impaired pancreatic β-islet cells and insulin resistance increase the likelihood of developing diabetes.^[27]

In individuals with blood sugar levels in the prediabetic range, weight loss was demonstrated to have many benefits including improved glycemic control and a reduced risk of developing type 2 diabetes.^[28]

Commonly associated with weight loss

Common gastrointestinal disorders associated with weight loss are malabsorption due to Celiac disease or chronic pancreatitis.^[5] Depression and eating disorders such as anorexia nervosa can also contribute to weight loss.^[5] Infectious causes of weight loss include HIV/AIDS.^[5]

While

As weight loss depends partly on calorie intake, different kinds of calorie-reduced diets, such as those emphasizing particular macronutrients (low-fat, low-carbohydrate, etc.), have been shown to be equally effective as weight loss tools.^{[29][30][31][32][33][34][35]} Nonetheless, a low-saturated fat diet complemented with high fiber can be helpful for those who are found to be obese based on BMI.^[12] Furthermore, a low-carbohydrate diet can have the added benefits of blood sugar control in those with Type 2 Diabetes Mellitus.^[12] A low-carbohydrate diet can also improve weight loss, HDL, and cholesterol in certain individuals.^[36] Compared to a typical diet, low-carbohydrate, low-fat, and moderate macronutrient diets can all positively impact weight loss.^[35] However, weight regain is common, and the outcome of a diet can vary widely depending on the individual.^{[12][30][33][37]} Rather than focusing on the nuances of each diet type, molding one diet in a way that the person can continuously adhere in the long-term could be beneficial for weight loss.^[5]

DASH diet

The Dietary Approaches to Stop Hypertension (DASH) diet focuses on increasing the consumption of fruits, vegetables, whole grains and low-fat dairy products.^{[12] [38][39]} DASH offers an intervention to manage elevated blood pressures and prevent cardiovascular disease non-pharmacologically.^{[39][40][41][42]} In addition, combining the DASH diet with a reduced sodium intake will further decrease blood pressure, but is not required for therapeutic effect.^[38] This is because it has been proven to be effective at a wide range of sodium intake levels.^[38] More recent reviews of DASH have continued to advocate its efficacy as an affordable weight loss tool, but stress that diet adherence is key to produce the desired results.^[43]

Mediterranean diet

The Mediterranean diet involves eating fruits, vegetables, whole grains and beans while replacing butter with extra-virgin olive oil and limiting red meats, dairy, sweets, and processed foods.^[44] It has been shown to be effective for long term weight loss with added cardiovascular health benefits.^[12][45] For example, the Mediterranean diet can lead to decreased triglyceride and lipid levels as well as improved blood pressure readings.^[34] It can also improve blood sugar levels in those diagnosed with Type 2 Diabetes Mellitus.^[34]

Ketogenic diet

The

The plant-based diet is largely based on consumption of beans, grains, fruits, and vegetables and removal of meat, fish, and occasionally dairy and egg products from intake.^[47] In other words, fiber and unsaturated fat intake is increased and consumption of higher calorie meats and saturated fats is decreased.^[47] This diet has been shown to reduce BMI and introduce positive body composition changes when compared to a carnivore diet.^[48]

Intermittent fasting

Intermittent fasting (IF) involves consistent fasting blocks of time where fewer or no calories are consumed.^[12] Intermittent fasting has been shown to improve fasting blood glucose levels and insulin resistance with a concurrent reduction in BMI.^[49]

Strategies

Modifying plate size

Some studies have suggested that using smaller plates might help people to consume smaller

The majority of guidelines agree that a calorie deficit, particularly 500-750 kcal daily, can be recommended to those who want to lose weight.[5]^[12] A moderate decrease in caloric intake will lead to a slow weight loss, which is often more beneficial than a rapid weight loss for long term weight management.^[8] For example, low fat meats reduce the total amount of calories and cholesterol consumed.^[53]

Increasing protein intake

A high protein diet relative to a low-fat or high-carbohydrate diet may increase thermogenesis and decrease appetite leading to weight reduction,^[54] particularly 3-6 months into a diet when rapid weight loss is observed.^[55] However, these advantages may be reduced later at 12–24 months into a diet during the slow weight loss phase.^[55]

Eating more soup

Studies have demonstrated that when compared to solid foods, soup ingestion decreases the amount of energy intake and increases feelings of satiety.^[56] When soup is consumed before a meal, there is a 20% decrease in the number of calories consumed during said meal.^[57]

Eating more dairy

Studies have shown that a diet high in dairy decreases total body fat.

Fruits and vegetables have been shown to increase satiety and decrease hunger signals.[63] These food groups have a low energy density, mainly due to the high water content and partly due to the fiber content.^[63] The reduction of energy density has been shown to enhance satiety.^[63] The water content adds satisfying weight without excess calories and fiber slows gastric emptying.^[63] Studies have also shown that fiber decreases hunger and also decreases total energy intake.^[63]

Increasing fiber intake

Fruits and vegetables are two sources of fiber as discussed above.

Due to the high volume or water content of fiber-rich foods, fiber displaces available calories and nutrients from the diet.

In general, large intakes of dietary fiber at breakfast have been associated with less food intake at lunchtime.[71] Fiber may have the added benefit of helping consumers reduce food intake throughout the day, but results of studies examining this possibility have been conflicting.^[70]

Increasing resistant starch intake

Resistant starch is a type of non-digestible,

Catechins are

While green tea intake alone may not significantly reduce weight or BMI, combining intake with other strategies aimed at weight loss could be helpful for both loss and weight maintenance. [91]

See also

• Anti-obesity medication
• Dieting
• Nutrigenomics
• Nutrition
• Weight loss
• Weight gain
• Orthorexia

References