Weight management
Weight management comprises behaviors, techniques, and physiological processes that contribute to a person's ability to attain and maintain a healthy weight. Most weight management techniques encompass long-term lifestyle strategies that promote healthy eating and daily physical activity. Weight management generally includes tracking weight over time and identifying an individual's ideal body weight.
Weight management strategies most often focus on achieving healthy weights through slow but steady weight loss, followed by maintenance of an ideal body weight. However, weight neutral approaches to health have also been shown to result in positive health outcomes.
Understanding the basic science of weight management and strategies for attaining and maintaining a healthy weight is important because obesity is a risk factor for development of many chronic diseases, like Type 2 diabetes, hypertension and cardiovascular disease.
Key factors
There are many factors that contribute to a person's weight, including: diet, physical activity, genetics, environmental factors, health care support, medications, and illnesses. Each of these factors affects weight in different ways and to varying degrees, but health professionals most often stress the importance of diet and physical activity because they can be affected by conscious behavior modification. Attaining a healthy weight involves recognition of general techniques such as portion sizing, self-monitoring, and daily diet consistency. Once this healthy weight has been attained, maintaining this stable weight additionally involves physical activity and control of an individual's environment and eating patterns. Furthermore, healthcare support in the form of primary care medical supervision and following up over time has been shown to be helpful for long-term weight management.The following is a review of some of the key components of weight management in humans.
Energy balance
The science behind weight management is complex, but one of the key concepts that governs weight management is Energy Balance. 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 in a given time period. There are three possible scenarios when it comes to the energy balance equation:- Calories consumed = Calories expended
- * 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
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. 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. Increased portion sizes may also lead to increased energy intake. Food categories such as intake of proteins, carbohydrates, and fats are all important to consider when managing weight. It is also important to have control and understand how certain foods may affect the human body.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. The specific type of activity can be tailored to populations such as children, pregnant women, and elderly adults. Tailored activity to one's fitness level also encourages the body to heal properly and prevent any injuries as a result of exercise.Physical inactivity leads to less energy expenditure and is a factor that impacts obesity rates in both children and adults. Physical inactivity has become a worldwide concern since inactivity also elevates the risk of heart disease. With a regular active lifestyle it can reduce the risk for noncommunicable diseases like diabetes, heart disease, and dyslipidemia. Physical activity not only reduces the risk of noncommunicable diseases, but it also can benefit the body such as improving sleep patterns, reducing both anxiety and depression, and of course, helps weight loss and weight management.
Basal metabolic rate
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 Rate 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.The BMR is directly proportional to a person's lean body mass. In other words, the more lean body mass a person has, the higher their BMR. BMR is also affected by acute illnesses and increases with burns, fractures, infections, fevers, etc. It can be measured via direct and indirect calorimetry. However, it is also possible to approximately estimate BMR using several equations that factor in a person's age, sex, height, and weight. Some of the most popular and accurate equations used to calculate BMR are the original Harris-Benedict equations, the revised Harris-Benedict equations, and the Mifflin St. Jeor equation.
The original Harris-Benedict Equations are as follows:
- BMR in Kcals/day = 66.47 + 13.75 + 5.0 - 6.76
- BMR in Kcals/day = 655.1 + 9.56 + 1.85 – 4.68
- BMR in Kcals/day = 88.36 + 13.40 + 4.8 – 5.68
- BMR in Kcals/day = 447.59 + 9.25 + 3.10 – 4.33
- BMR in Kcals/day = 9.99 + 6.25 – 4.92 + 5
- BMR in Kcals/day = 9.99 + 6.25 – 4.92 – 161
Body mass index
Body mass index 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 and weight :or
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:
| Category | BMI |
| Underweight | < 18.5 |
| Normal Weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity | 30.0 – 34.9 |
| Obesity | 35.0 – 39.9 |
| Obesity | ≥ 40.0 |
On average, groups of people with "obese" BMIs may have a higher risk of developing illnesses like diabetes, hypertension, dyslipidemia, 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.