The winter months are (almost) upon us, and with the change in season comes change in the way we eat and our physical activities (hygge is happening). Holiday meals are on the agenda, and maybe thoughts about weight are creeping in. You’ll often hear people say “Oh, Suzy can eat anything, she has a fast metabolism” or the opposite “Bob has a slow metabolism, he puts on weight just looking at pie.”
To better understand how metabolism really works, it’s important to understand what it is. It’s not just how quickly we digest a meal, or how much energy we have to make snow angels. Or what happens when that piece of pie comes into our field of vision.
Metabolism is the process of chemical reactions by which our cells change the food we eat into energy to fuel daily living. The metabolic process actually includes two main types of reactions, both critical to maintaining life: catabolic and anabolic.
- Catabolic reactions break down molecules in food and drink to obtain energy, such as when digesting a meal
- Anabolic reactions use the energy produced by catabolism to build larger molecules from smaller ones, i.e. building muscle
Ideally, catabolic and anabolic reactions would be in balance, with energy produced through catabolism being used through anabolism. If catabolic reactions produce more energy than the anabolic reactions can use, the body builds fat molecules to store the excess. If, on the other hand, catabolic reactions release less energy than the anabolic reactions use, the body turns to stored energy for fuel.
The Role of Hormones and Enzymes in Metabolism
Metabolic processes are controlled by catabolic and anabolic hormones and enzymes in the body.
Catabolic hormones like cortisol, glucagon, adrenaline/epinephrine, and cytokines, stimulate the breakdown of molecules and the production of energy. The hormones are mobilized at specific times according to the demands of the body.
Anabolic hormones are necessary for the synthesis of molecules, and they include insulin, growth hormone, insulin-like growth factor, testosterone, and estrogen.
Metabolic enzymes are controlled by the catabolic and anabolic hormones, and include lipase, amylase, protease, trypsin, tRNA-ligase, DNA polymerase, antioxidant enzyme, glucoamylase, and many more.
As you can imagine, in such a complex and crucial physiological process, things don’t always operate perfectly. Having a consistent mismatch between food intake and energy output is a primary cause of the rise of diabetes and obesity in North America. More rarely, malfunctions or errors in metabolic processing, where the body has an imbalance in an important metabolic element, can also lead to such conditions. These malfunctions are often the result of a genetic alteration or mutation, and are typically hereditary.
In conclusion, metabolism is a very complex process, and is not likely to be affected by looking at a piece of pie. So eat the piece of pie, get up and get moving and, in the absence of any disease, your metabolic system should be flexible enough to accommodate a few days of holiday indulgence!