When most people start dieting, they slash their calories and add a large amount of exercise to their daily routine. That’s fine, but they usually cut their calories way too low. Add in the extra exercise, and all of a sudden you have an extreme calorie deficit that is working against you.
Not eating enough calories causes many metabolic changes. Your body is a smart machine and senses a large decrease in dietary energy. Your large calorie deficit might work for a few days or even weeks, but eventually your body will wake up and sound alarms that it needs to conserve energy.
It doesn’t want to just waste away. It needs that energy (fat) to survive. So, what does your body do when it senses prolonged energy restriction? Not eating enough calories…
- Slows down thyroid production – Your thyroid is responsible for fat, carbohydrate, and protein metabolism, among other things. Your body has the ability to slow down thyroid output in an effort to maintain energy balance.
- Decreases muscle mass – Muscle is highly calorie intensive to maintain. In a prolonged extreme calorie deficit, it is one of the first things that your body looks to get rid of, especially if you’re not providing a stimulus to keep it. Your body needs the fat, wants the fat, and the muscle can be spared. It breaks down the muscle tissue and uses it for energy.
- Lowers testosterone levels – An important hormone for both men and women, testosterone is just one of many hormones that are affected with severe calorie restriction. Testosterone is anabolic to muscle tissue. Without it, it becomes that much harder to maintain, let alone put on muscle mass.
- Decreases leptin levels – Leptin is one of many energy regulating hormones. More importantly, it’s a “hunger” hormone that tells you whether to eat or not. High leptin levels signal that it’s OK to stop eating, while low leptin levels are a signal to eat more energy. Because of this, leptin levels decrease in calorie restricted environments.
- Decreases energy levels – There are many physical actions your body takes when you’re not eating enough calories, but there are also some mental ones. Neurotransmitter production is limited, which can lead to a lack of motivation. It’s your body’s way of telling you to “slow down” – conserve your energy.