Slower metabolism and weight gain
Many people who want to lose weight as fast as possible will put themselves on a restrictive, extremely low-calorie diet. While this seemingly quick fix may work initially, it turns out that not eating enough calories will likely lead to a slower metabolism in the long run, making it harder to lose weight and keep off the weight you've already lost. For this reason, weight regain (or even gaining additional weight) is a common, surprising downfall of low-calorie diets.
Essentially, when your body isn't receiving enough energy from the food you're eating, it will quickly adapt by storing as much of the energy it does get as possible. This leads to a slower metabolism. "The body realizes that there aren't enough calories to fulfill all its needs so it clings on to the little bit that does come in and can cause weight gain," Garcia explains.
Lippert breaks down this process: "Over a short period of time, the body slows down the metabolism, heart rate, and more to accommodate the lower intake of fuel and nutrients and optimizes bodily functions with the lower calorie intake," she explains.
This can be detrimental to your weight loss goals. Once your metabolism has slowed due to a restrictive diet, it can be hard to boost it again. "When a person leaves a low-calorie lifestyle and returns to their normal eating patterns, the body is still in a state of running off of less calories, thus it stores all the excess fuel that is consumed compared to what it had received in the lower caloric state," Lippert says. "It is very difficult to increase the metabolism back to where it was prior to the lower-calorie diet and this leads to weight gain."
So, while the number on the scale may go down within the first few weeks of your crash diet, remember that it likely won't be worth it in the long run.
Weaker immune system
In addition to unwanted weight gain, low-calorie diets can also lead to other serious health complications. That's because our immune systems rely heavily on the nutrients we get from our diet. If we aren't consuming enough calories, we're not getting enough of those nutrients, and our bodies become extremely vulnerable due to a weaker immune system.
Garcia says eating enough food is essential to our overall health and all of our body's functions. She notes that ample nutrition is vital when it comes to "repairing and rebuilding of cells in the body, including the cells that fight infections, illnesses and anything that may cause harm to the body." Without the ability to repair those cells, we're at serious risk.
"A low-calorie diet may be lacking in nutrients and can lead to deficiencies in the body that support the immune system as well as many other bodily functions," Lippert agrees. "If the body does not receive sufficient fuel or nutrients to support the immune system, it may weaken the response of the immune system, putting you at an increased risk of infection."
If you ask us, a slightly lower number on the scale doesn't seem worth those health risks—especially when you consider the fact that your weight loss will likely be short-lived.
If you really want to lead a healthier lifestyle rather than just falling victim to a crash diet, it's important to prioritize proper nutrition on your weight loss journey. In fact, Lippert says she oftentimes recommends adding more nutrients to her clients' diets. "In order for the body to do everything from breathing, digesting, healing and detoxifying, it requires energy and nutrients, which comes from the foods we eat," she says.
While a balanced diet that provides ample calories may take longer to produce results, in the long run, it's a much healthier, safer, and sustainable way to lose weight. In the end, your body, metabolism, and immune system will thank you for it.