You have more on Saturdays than Mondays, it seems to evaporate just before any planned gym sessions, and kids on airplanes have a seemingly endless supply. Energy sustains life, and despite what you may think when you\’re drained at the end of a working day, our bodies are extraordinary engines that continuously produce, use and manage this resource.
At its most basic level, the process is quite simple. We eat, food is digested and energy is produced. Professor Shane Norris, director of the Department of Science and Innovation (DSI)-National Research Foundation (NRF) Center of Excellence in Human Development and the Medical Research Council (MRC)/Wits Developmental Pathways for Health Research Unit (DPHRU) explains: \” Food has energy locked up in the three macronutrients: proteins, fats and carbohydrates. [The vitamins and minerals in food are called micronutrients]. After the food has been digested and broken down into its most basic components, the glucose is extracted from the macronutrients and used by the body for fuel.\”
Whether it\’s fat, protein or carbohydrates, the body breaks down food into the same energy component: glucose, the main sugar found in the blood. But glucose is actually quite toxic, Norris says, so the body must constantly balance glucose demands, use, and excess. To do this, the pancreas regulates levels of the hormone insulin, which \”pushes\” glucose out of the circulation and into the muscles and fat cells.
Energy intake
But the body is a complicated machine, and it\’s not as simple as \”food in, energy out.\” Although it can extract and use glucose from all macronutrients, the body prefers to use carbohydrates for energy, says Dr. Thanujj Kisten, professor of nutrition, exercise and energy at the School of Physiology.
\”All macronutrients can be a source of energy, and fat actually contains the most energy. But fat and protein take much longer to break down, so the body prefers carbohydrates. The brain can\’t use them directly fats as an energy source and proteins are used as a last resort because it has more important roles as a catalyst for chemical reactions.Unfortunately, the diet industry has created this misconception that all carbohydrates are bad.Simple carbohydrates carbohydrates like refined sugar are actually processed very quickly, leading to a big spike in energy and then a crash.But complex carbohydrates like brown rice are broken down more slowly, resulting in a gradual and sustained release of energy.
But even when carbohydrates are unavailable, the body will continue to function by converting fat and protein for use as energy. “This process takes longer, which is why people on keto diets [a popular low carb/high fat weight loss diet] he will often feel lethargic,” says Kisten.
When you eat also plays a role in energy levels throughout the day, she adds. \”Not eating breakfast, for example, could cause lethargy [fatigue] as your body does not have readily available fuel. Research shows that having five smaller meals a day, instead of three large meals, provides more sustained energy throughout the day.\”
Energy expenditure
Even when you spend all day watching television from your couch, your body uses about 8,700 kilojoules a day to keep you alive. The brain uses the largest portion of this number than any other organ, Norris says. \”So, functional systems like the cardiovascular and digestive systems take their toll, maintenance systems that repair or create cells further deplete available energy, and the immune system uses some energy to prevent disease and more when fight an infection.
\”Any unused energy is then stored as body fat to be used when extra fuel is needed.\”
Activity, of course, alters energy expenditure. A five-kilometer run, for example, burns between 1,300 and 1,500 kilojoules in a person of average height and weight. So if physical activity burns energy, why do experts recommend exercise to boost energy levels?
\”In the short term, exercise uses up energy, and you may feel fatigued later on,\” says Kisten. “But in the long run, exercise teaches the body to use energy more efficiently. Over time, it begins to use less energy to carry out normal daily activities, leaving you more energetic. This effect can take two weeks to two months before it occurs, depending on the type of exercise and frequency.\”
Find the balance
There is no one-size-fits-all energy model, says Kisten. “A professional athlete will have a much higher energy requirement than someone in a desk job. The heavier you are, the more energy your body requires to move. This is one reason why an obese person might fatigue faster than a healthy weight. Conversely, those who are underweight will not have enough fuel and will also suffer from fatigue.\”
Your energy needs will depend on your health and wellness goal, and there are many nuances and considerations. According to a Wits Sport and Health (WiSH) webinar, energy availability in athletes can be affected by a number of health factors, some normal, such as female hormones that regulate the menstrual cycle, others problematic, such as iron deficiency or psychological problems. \”And more recent research shows that even weight loss isn\’t as simple as once believed,\” says Norris.
“Any diet that creates a kilojoule deficit will ultimately result in weight loss, even though some are healthier than others in the long run. But we are now realizing that a kilojoule deficit creates a biological response to stress. The body recognizes that something is wrong when weight loss occurs, and activates stress hormones to slow metabolism, while addiction-associated brain centers fire up to increase appetite.Eventually, you will lose weight, but your body tries to fight you along the way.
\”On a global scale, obesity is now a bigger problem than hunger and will be for a long time,\” says Norris. In a three-generation cohort study, increased risk of cardiovascular disease persisted in grandchildren of obese individuals.
\”Whether you\’re vegan, vegetarian, meat eater or live on simple carbohydrates, sourcing is no longer the world\’s biggest problem. Now it\’s about socioeconomics: can you afford healthy food and are you getting the nutrients you need? Our work in Soweto shows that around 20% to 36% of adults are anemic, meaning they don\’t have enough iron to make blood cells. The challenge today is not to have more, but to find the balance.\”
How accurate is the paleo diet?
The premise of one of today\’s most popular diets, the paleo diet, is that modern eating habits are so far removed from those of our ancestors that our bodies couldn\’t keep up, resulting in health ailments and weight issues. Eliminate everything that is \”processed\”, even some crops produced by modern agriculture such as cereals and legumes.
How accurate is it? Simply put, it\’s not, says Dr. Christine Steininger, director of the Genus project: DSI-NRF Center of Excellence in Paleosciences. “Our ancestors also ate processed foods. Later, Homo sapiens used fire, a processing method, to make food more palatable and to kill microbes. And as our diets evolved, our gut It has evolved.
Our ancestors in South Africa, the most common of which was Australopithecus africanus, ate more like chimpanzees between 4 and 1.9 million years ago, he says. “They ate what was in their immediate environment, such as fruits, nuts and insects. Early Homo habilis, between 2.4 and 1.6 million years ago, began using tools to eat mammalian remains such as bone marrow, probably digging it up, and the extra protein increased their brain size.So Homo erectus, our earliest known upright ancestors, were possibly migratory hunters, and the extra protein made them taller and stronger.The diet has played an important role in evolution.
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