If you’re determined to drop some weight RIGHT NOW then you might be thinking that a crash diet is your best bet. Although there is no medical definition of a “crash” diet, most folks equate them with rapid weight loss due to extreme caloric restriction. Sometimes rapid weight loss diets are physician supervised and tightly controlled and undertaken for health reasons that require quick weight loss progress. More often though, extreme diets are a go-it-alone process, and that’s when things can go off track and head into dangerous territory; here are a few reasons why…
You restrict calories too low.
Consuming just 800-1,200 (or even 1,500 calories if you’re larger or physically active) makes it really difficult to get in all the nutrients your body needs each day. You’ll need to be really on top of your food intake and plan very carefully—and even then you likely will fall short in something. Aside from that, you’ll likely feel lethargic because your body doesn’t have the caloric energy it needs. A very low calorie intake even impacts your mental sharpness.
Your crash diet turns into a long-term thing.
As a dietitian, I do not advise “crash dieting” at any time—it’s better to have a sensible, more moderate plan in place for shedding excess fat. In the very short term (such as 2-3 days) however, you’ll likely be fine as long as you are already a healthy person, you stay well hydrated and don’t have any contraindications (such as pregnancy, diabetes, are a child/teen/elderly person, etc). Much longer than this, however, can lead to nutrient depletion that can have real health impacts, including slower metabolism, muscle loss, vitamin and mineral deficiencies, GI problems, blood pressure and electrolyte imbalances and other consequences such as depression.
You don’t realize that you’ve developed disordered eating tendencies.
Maintaining tight control over your food intake requires a lot of mental commitment. Sometimes the eating plan takes over your life without you even realizing it. Think about all the time and effort it takes to do things like plan your daily food intake, log or track your food, strategize when you’ll eat and how your food intake will fit into your schedule, research appropriate recipes or specific foods to fit your plan, etc. All of this work can lead to symptoms of disordered eating, which includes things like feeling shame when you are unable to follow your plan; a preoccupation with food, your body or exercise; and feeling like you need to somehow compensate for the food you eat (such as by exercising more). While clinically diagnosed eating disorders and disordered eating are not exactly the same thing, having disordered eating can be dangerous, too. (Here is a helpful link with information on where to go for help if you feel your dieting or that of a friend or loved one has gotten out of control and morphed into disordered eating.)