Catabolism, or destructive metabolism, is the process that produces the energy necessary for all the activity that takes place in cells. Cells break down large molecules (mostly carbohydrates and fats) to release energy. This provides fuel for anabolism, warms the body, and allows the muscles to contract and the body to move.
When complex chemical compounds are broken down into simpler substances, the body expels waste products through the skin, kidneys, lungs, and intestines.
What controls the metabolism?
Several hormones in the endocrine system help control the speed and direction of metabolism. Thyroxine, a hormone made and released by the thyroid gland, plays a crucial role in determining how quickly or slowly metabolic chemical reactions occur in a person’s body.
Another gland, the pancreas, secretes hormones that help determine whether the body’s main metabolic activity at any given time is anabolic or catabolic. For example, there is usually more anabolic activity after eating. This is because eating food increases the blood level of glucose, the body’s most important fuel. The pancreas senses this higher concentration of glucose and releases the hormone insulin, signalling the cells to increase their anabolic activity.
Metabolism is a complicated chemical process. But it is not surprising that many people simplify it and only see it as something that influences how easily our body gets fat or thin. This is where calories come into play. A calorie is a unit that measures how much energy a particular food provides to the body. A chocolate bar has more calories than an apple, providing more energy to the body, although calories should not be exceeded. Just like a car stores gasoline in its tank until it needs it to power the engine, the body stores calories, mainly in the form of fat. If we fill the tank of a car too much, the gasoline overflows and spills on the ground. Similarly, if a person eats too many calories, they “overflow” and generates excess body fat.
The number of calories a person burns in a day is affected by the amount of physical exercise, the amount of fat and muscle their body has, and their basal metabolic rate. Basal metabolism measures the rate at which a person “burns” energy in the form of calories while at rest.
Basal metabolic rate can influence a person’s tendency to gain weight. For example, a person with a low basal metabolic rate (who therefore burns fewer calories while resting or sleeping) will tend to gain more pounds of body fat over time than a person of similar size with an average basal metabolic rate who eats the same amount of food and get the same amount of physical exercise.
Basal metabolism can be affected by a person’s genes and by some health problems. The physical constitution also influences it: people with more muscle and less fat tend to have higher basal metabolic rates. But people can change their basal metabolism in specific ways. For example, a person who does more physical exercise will burn more calories and improve their physical form, which will increase their basal metabolism.
Effects of the results on drug dosing and cancer treatment
Experts say that this new understanding of metabolism will have implications that go beyond weight management. For example, there may be applications for drug dosing concerning the rate at which the body metabolizes medication. Methods of treating diseases like cancer could also change, says Pontzer. “Tumor cells metabolize energy as they grow and multiply,” she notes. “Therefore, cancer may progress differently in younger people with faster metabolism compared to older people with a slower metabolism.”
The study also provides new information on the ageing process, specifically on changes in cellular activity that occur with age. “There is age-related deterioration that occurs in every system in the body,” says Pontzer. “One of the most interesting aspects of the study is that we now have a map of how this change occurs at the metabolic level because metabolism is an indicator of the body’s activity.”
By better understanding the cellular changes that occur with age. According to Rozalyn Anderson, a professor at the University of Wisconsin School of Medicine and Public Health, older adults’ vulnerability to disease studies the biology of ageing.
“Around age 60 is when we begin to see the appearance and increased risk of age-related disorders, such as cancer, cardiovascular disease or neurodegenerative diseases,” says Anderson. “When I saw these data, I was immediately struck by the fact that there is also an intrinsic change in innate metabolism that begins at the same time.”
In the future, the research could delve beyond the first level of population data, perhaps classify study participants based on their metabolism and determine if there are differences in the outcome of their disease. “To what extent does individual metabolism before age 60 dictate the rate of change after age 60?” Asks Anderson. “As metabolism slows in adulthood, can a steeper rate of decline be linked to a higher incidence of disease?”
Ferrante argues that the research provides a firm foundation for scientists to undertake many other studies. “This is a significant observational study, but it doesn’t delve into the why’s,” she says. “Now, we can begin to answer those questions.”