“Our bodies more or less tell us what to eat and when to eat it, so maybe we should just follow that,” says Susanne Krauss, lead researcher at the German Institute of Human Nutrition.
That makes sense, but the way our bodies require energy isn’t the same throughout our lives.
Whether it was being spoon-fed by our parents as toddlers, sneaking sweet treats as a child, eating everything in sight as a teenager, then nibbling away at small, simple plates later in life, our appetites change as we age, and understanding why can help us stay healthy in later life.
Hunger hormones and their functions
In essence, eating food is functional: without the energy we get from food, we cannot survive.
The carbohydrates in food are converted into energy, while the fats and amino acids help make important proteins and other structures that help the body function.
To ensure that these processes run like clockwork, the body has special systems that ensure a regular supply of energy.
“these [are self-regulating] “The mechanisms that trigger hunger and satiety are primarily signals from the stomach and intestine, but also from hormones such as leptin secreted by adipose tissue. [or body fat] This then sends a signal to the hypothalamus. [a control center in the brain]This is the autonomic nervous system, like breathing.”
These chemical motivators that compel us to seek (or stop seeking) food are sometimes called the hunger hormones. Besides leptin, ghrelin is probably the best known hunger hormone.
Ghrelin is released into the bloodstream from the stomach to tell the brain to eat, and when you’re full the release of ghrelin slows down, giving you a feeling of fullness.
Other hormones also regulate satiety and hunger, including insulin and other pancreatic hormones that suppress hunger, such as GLP-1, which the diabetes drug Ozempic mimics.
How Digestion Works
When these hormones prompt you to put food in your mouth, your body uses the digestive process to literally eat up the food.
Mechanical digestion begins in the mouth, breaking down food into small enough pieces to swallow. This process continues until swallowed liquids are forced down the esophagus into the stomach. This process is known as peristalsis.
Parallel to this process, chemical digestion takes place. This begins in the mouth, where the amylase enzyme in saliva begins to break down the starches in the food. More digestive enzymes finish digestion in the stomach, and water and nutrients are absorbed from the intestine into the bloodstream.
How does appetite change with age?
Puberty is when your appetite skyrockets as your body craves the energy it needs to complete the most crucial stage of development, puberty, and propel you towards physical and sexual maturity.
But nutrition across the lifespan can be difficult. As we age, we’re at risk for our bodies becoming less efficient at helping us get the nutrients we need. Some research suggests that hunger hormone secretion patterns change as we age.
“On average, as people get older, [they] “You lose muscle mass, and muscle is where you burn the most energy,” Krauss said.
The main cause of muscle mass loss is not eating enough protein.
“Protein intake in older adults is lower than recommended and according to various scientific bodies even the recommended protein intake in older adults should actually be higher because maintaining muscle mass is so important,” said Daniel Crabtree, a geriatric nutrition researcher at the University of Aberdeen.
Despite this advice, older people tend to consume less protein than recommended amounts, which Crabtree said could be due to physiological factors and other signs of physical ageing, from dental problems to changes in taste and smell.
Editor: Zulfiqar Abani
