Hormonal changes
Our bodies rely on calories to carry out a number of important functions. While Doebrich notes that a small calorie deficit is necessary for weight loss, she says denying your body a sufficient amount of calories is detrimental to your health. “If we go too low, we are putting our body in a state of emergency,” she warns.
Our bodies will perceive a large calorie deficit as starvation and activate emergency responses. For women especially, these emergency responses often come with hormonal changes, leading to issues such as irregular periods, decreased bone density due to lower estrogen, and unwanted fat accumulation in the abdominal area caused by high cortisol levels.
“Female hormones alter the way fat is stored, and especially in times of stress, hormones are released that make us hold on to energy and slow down metabolism,” Doebrich says.
Metabolism changes and weight gain
Doebrich explains that your body’s metabolism will begin to decrease dramatically even after the first few weeks of a restrictive diet. “You are now so starved of energy that your body will store any form of energy immediately in preparation for the next period of starvation,” she explains. “It’s inconvenient but actually pretty impressive how much our body works to protect us from starving.”
For this reason, a restrictive diet likely won’t help with long-term weight loss. “Very low-calorie diets usually work for a very limited time, after which the body becomes so inefficient at metabolizing energy that we hit a plateau,” Doebrich says.
Additionally, you may start to crave high-calorie, fatty foods when you deny your body a sufficient amount of food each day. These are just a few reasons why crash diets will eventually end in the opposite of their desired results: weight regain.
Nutrient deficiency
Providing your body with all the nutrients it needs to keep everything running smoothly and healthily is integral to your wellness–and it’s impossible to do that if you’re not eating enough. “Nutrients are needed for many key functions and the only way to get enough of them is by eating food consistently,” Doebrich says.
From thinning hair to mood disorders, Doebrich explains that nutrient deficiencies can lead to a plethora of health issues; the exact problems you may experience will depend on the amount of nutrients you’re missing. “Very low calorie diets usually make it impossible to meet needs for iron, calcium, fiber, vitamin B12, vitamin D, or zinc to name a few,” she says.
The bottom line
While you may see the number on the scale go down for the first few weeks of your restrictive diet, the adverse effects of denying your body energy and nutrients simply won’t be worth it in the end.
So, what is the best way to lose weight? According to Doebrich, it’s with a small deficit of about 200-300 calories each day. This will help you lose weight in a healthy way, even if you’re consuming 2000 or more calories daily
“In many cases this type of deficit is much more effective because your body is not feeling threatened and doesn’t activate all these emergency responses,” Doebrich says. “It may take longer than the crash diet that restricts calories to an extreme but it will pay off in the long-term.”