Why Crash Diets Are SO Bad For You— (And It’ll Make You Fat Too)

Juice fasts that last longer than three days are really bad for your body. Image by Inyucho via Wikimedia

Juice fasts that last longer than three days are really bad for your body.
Image by Inyucho via Wikimedia

It makes me so upset when one of my clients announces they’ll go on this juice fast or that extreme low carb diet for the next couple of weeks or so. Yes, they will lose weight— IF they manage to reach the end of the diet. But almost always they’ll regain the weight and, what’s worse, they’ll gain more, ending up heavier than when they started. A precious few will keep the weight off, but that is because they changed their lifestyle permanently after the crash diet.  And, in my experience, this rarely happens (people are just way too hungry). Even if they do manage to keep the weight off, is that rapid weight loss worth all the damage it does to your body?  After you read below article by Martha McKittrick, NYC’s best nutritionist, you may see why it upsets me so much when my clients crash diet:

Possible serious health risks from rapid weight loss

We all know that being at a healthy weight can decrease your risk of numerous diseases. But it’s not worth risking your health to get there quickly. In addition to losing calorie burning muscle, rapid weight loss can cause the following:

– Gallstones, which occur in 12% to 25% of people losing large amounts of weight over several months (reference)


– Malnutrition, usually from not eating enough protein for weeks at a time

– Electrolyte imbalances

Do you really want to lose your hair? I didn't think so.

Do you really want to lose your hair? I didn’t think so.

– Headaches

– Irritability

– Fatigue

– Dizziness

– Constipation

– Menstrual irregularities

– Hair Loss (reference)

– Muscle loss. When you are on a weight loss diet, you actually need more protein than if you weren’t dieting.  And because most very low calorie diets don’t meet your protein needs, your body ends up breaking down its own muscle mass to use for fuel.  Even if you were to consume adequate protein,  your body would still break down muscles for energy if your caloric deficit is too great.

– Decreased testosterone levels in men

Note: some people are advised to lose weight quickly for health reasons and are prescribed a medically supervised Very Low Calorie Diet (VLCD). While health risks are still there, it’s not as dangerous as doing it on your own as you are being monitored by a doctor.

More about rapid weight loss diets
Most rapid weight loss diets are very low in calories and carbs, as well most other nutrients.  It’s pretty much impossible to consume a nutritionally balanced while consuming 500-1000 calories a day! Some crash diets are liquid fasts, some are mainly protein based while others allow only a few foods.  The longer you follow this kind of diet, the greater the health risks can be.

Keep in mind that it is not unusual to lose 3-8 pounds the first week of a low carb diet. That’s because carbs hold onto water.  So when you cut them out, you lose pounds of water quickly. After the initial water loss, most experts recommend losing 1-3 pounds a week (the smaller you are, the less you should lose). Losing much more than this can lead to the previously mentioned problems.  I generally recommend that you don’t consumer fewer calories than your basal metabolic rate (BMR). Calculate your BMR here.

Tips to minimize dangers from diets promoting rapid weight loss
My first tip is to avoid them. Chances are that every pound you lose this way will come back on! But if you feel the NEED to jumpstart your weight loss, here are some tips:

1. If you have a medical condition or are taking medications, check in with your doctor first prior to starting a diet.  Also, avoid taking any herbs or supplements until checking in with your doctor as some can interfere with medications.

2. Cutting down on carbs and sodium can promote a rapid weight loss initially. This can help to motivate you. But after 2 weeks or so, slowly add some carbs back in to make the diet healthier and more realistic

3. Stay hydrated. Drink at least 8 cups of fluid a day.

4. Consume adequate protein. A general recommendation is ~ 70 – 100 grams a day. This can help to slow (but not prevent) the loss of muscle mass that occurs when following a low calorie diet.

5. Minimize the time you follow  a very low calorie diet. The longer you follow it, the more you will slow your metabolism and deprive your body of nutrients. Keep in mind that this is one time that “slow and steady wins the race”!

Have any of you tried a very low calorie diet? How did you feel and what were the results?

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