Metabolism: Myths and facts
Sign up for a free Medical News Today account to customize your medical and health news experiences. These biochemical processes allow people to grow, reproduce, repair damage, and respond to their environment.
It is a common belief that slim people have a higher metabolism and overweight people have a slower metabolism. In fact, this is very rarely the case. This MNT Knowledge Center article will discuss the facts behind metabolism, what it is, what it does, and how it is influenced. Despite what promoters of certain brands of "health" foods say, there is little people can do to significantly change their resting metabolic rate.
However, determining a body's energy needs, then adapting lifestyle accordingly, will have a quicker effect on altering body weight. Anabolism is the building up of things - a succession of chemical reactions that builds molecules from smaller components; anabolic processes usually require energy.
Catabolism is the breaking down of things - a series of chemical reactions that break down complex molecules into smaller units; catabolic processes usually release energy.
Anabolism allows the body to grow new cells and maintain all the tissues. Anabolic reactions in the body use simple chemicals and molecules to manufacture many finished products. Examples include the growth and mineralization of bone and increases in muscle mass. Catabolism breaks things down and releases energy; it uses larger compounds to create smaller compounds, releasing energy in the process. Catabolism provides the energy our bodies need for physical activity, from cellular processes to body movements.
Catabolic reactions in the cells break down polymers long chains of molecules into their monomers single units. When we eat, our body breaks down nutrients - this releases energy, which is stored in molecules of adenosine triphosphate ATP in the body.
ATP is considered to be "the energy currency of life. The energy stored in ATP is the fuel for anabolic reactions. Catabolism creates the energy that anabolism consumes for synthesizing hormones, enzymes, sugars, and other substances for cell growth, reproduction, and tissue repair. Body weight is a result of catabolism minus anabolism - the amount of energy we release into our bodies catabolism minus the amount of energy our bodies use up anabolism.
The excess energy is stored either as fat or glycogen in the muscles and liver. Glycogen is the main storage form of glucose in the body. One gram of fat produces 9 calories , compared with 4 calories from a gram of protein or carbohydrate.
Although becoming overweight is a result of the body storing excess energy as fat, sometimes, hormonal problems or an underlying medical condition may affect metabolism. If someone is very overweight or obese, it may be advisable to have a medical evaluation to determine whether a medical condition is affecting body weight.
BMI is an evidenced-based way to calculate ideal body weight ranges for age and height. A larger body mass requires more calories.
People with more muscle in relation to fat will require more calories than individuals who weigh the same but have less muscle in relation to fat. Therefore, people with a higher muscle-fat ratio have a higher basal metabolic rate than people with a lower muscle-fat ratio, if their weight is the same. As people age, several factors emerge that result in a lower calorie requirement.
Muscle mass drops, resulting in a higher fat-muscle ratio. Also, the following age-related factors reduce a person's calorie requirement:.
After determining calorie requirements and confirming that there is no underlying condition contributing to weight gain, focusing on three crucial factors is the best approach; these are:. Lack of sleep can contribute to a disturbance in neuroendocrine control of appetite. This may lead to overeating, altered insulin resistance , and an increased risk of developing type 2 diabetes - all of which can lead to weight gain. Several studies have shown that sleep deprivation damages the body's ability to regulate eating by lowering levels of leptin, the hormone that tells the body when it is full.
A 6-month trial carried out by researchers from Duke University Medical Center studied the impact of exercise on 53 participants who led a sedentary lifestyle. The trial measured the impact of four levels of physical activity: Significant benefits were noted in the exercise groups.
Importantly, only a moderate amount of exercise was needed to show benefit. The best way to improve diet and nutrition is to eat plenty of fruits and vegetables. Managing the number of calories consumed each day is an important factor in weight control, especially if attempting to lose weight. However, severe calorie restriction has been shown to be ineffective for long-term success. A severe drop in calories may trigger the body to alter its metabolism so that much less energy is burned, while at the same time storing any energy it can find.
Very low-calorie diets commonly undermine motivation, resulting in overeating when the diet is abandoned. Unless the very low-calorie diet is being supervised by a well-qualified dietitian, nutritionist, or doctor, there is a significant risk of malnutrition , which is not only detrimental to health, but may also affect metabolism in a way that makes it more difficult to achieve weight loss.
Article last updated on Tue 18 July All references are available in the References tab. How many calories equal one pound?
Exercise reverses unhealthy effects of inactivity. Role of sleep and sleep loss in hormonal release and metabolism. The link between short sleep duration and obesity: Archives of Disease in Childhood. Sleep may be factor in weight control. MNT is the registered trade mark of Healthline Media. Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a healthcare professional.
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Register take the tour. Table of contents Metabolic rate What is metabolism? Body weight Calorie requirements Losing weight. Fast facts on metabolism: When people use the word "metabolism" they are often referring to catabolism and anabolism. Catabolism is the breaking down of compounds to release energy.
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