Do Crash Diets Get The Green Light?

by Denis Faye | October 17, 2014

a83eca15e5f5f296ce5f25f8fe28e27dIf you’re willing to swallow a new study from Down Under, it looks like “crash diet” is no longer a dirty word. (Technically, it’s two words, but you get my point.)

Researchers at the University of Melbourne split obese people into two groups. One group dieted using a conventional gradual diet for 36 weeks with a 500-calorie deficit. The second group did a “very low calorie diet” for 12 weeks at 450 to 800 calorie total daily. (Not a 450-800 calorie deficit. Rather, that’s how much they ate each day. This is different from just a “low calorie diet” which would be 800-1200 calories daily. )

50% of the gradual folks lost 12.5% of their body weight. 71% of the very low calorie folks did the same. The researchers then gave all these 12.5-percenters a 3-year maintenance diet to follow.

After those 3 years, both groups regained about 71% of their weight back.

The take away? Well, the study’s authors concluded that this means crash dieting is every bit as effective as gradual dieting. And I agree–provided, of course, you live an plastic science bubble where real world factors don’t count.

Here’s a better take away: “Both gradual and crash diets (which should only be attempted by obese people because a normal person without adequate fat stores could die eating 450 calories a day for 94 days) are ineffective unless people rethink their relationship with food following the diet.”

Unfortunately, that’s kind of a mouthful and most Cosmo readers would tune out by the word “attempted,” instead clicking through to 67 Blow-His-Mind Moves. (69 would been more logical, in my opinion. Too obvious?)

Lifestyle magazines and blogs will now delight in “debunking the myth” that crash diets are less effective than gradual diets–which is click-grabbing puffery considering the general scientific community has been okay with the scientific community has been okay with very low calorie diets for decades now. It’s not the physical act of undereating for the brief period of time that’s the issue. It’s the psychology around it that’s problematic. In the two decades I’ve spent helping people lose weight, I’ve noticed two things about crash dieters. First, they usually have a short-term goal in mind. Oftentimes, it’s a wedding. The diet industry wouldn’t exist if it weren’t for matrimony. And much like a modern marriage, dieters rarely seem to care if they can maintain what they achieved leading up the the ceremony. They don’t have a plan, so it all falls apart.

Second, crash dieters often don’t care about the quality of the food they eat. They just want to find the most tolerable way to eat as little as possible in the shortest amount of time. Because this, they don’t learn how to create a sustainable diet, so when they’re done, they fall on old, bad habits, like philandering and watching stag films and leaving their underwear on the kitchen counter–no, wait, that’s the marriage thing again. Either way, you get the point. While the physical act of crash dieting may be no less effective (for obese people) than gradual dieting, the motivation behind it is often shortsighted and dooming it to failure.

And for the record, if you’re not obese, excessively low calorie diets can tear your body to pieces, almost literally. You won’t have the adipose tissue (body fat) to maintain the 1,300-odd calories most people need to just stay alive each day, so you’ll start auto-cannibalizing, or breaking down muscle and other lean tissue to survive.

Under medical supervision, there’s a place in the dietsphere for very low calorie diets. There’s even some cool research emerging out of England showing their benefits on (obese) type two diabetes sufferers.

And if you’re not obese, I grudgingly admit that it’s probably okay to try 800-1200 calories for brief periods of time. It’s certainly not my thing, but sometimes, folks want to get thinner quick-like. (I’ve worked on a couple programs at Beachbody that allow you to do this without impacting muscle mass too badly.) But if you’re going to do that, it needs to be part of a bigger, long-term plan. If you want to do it right–and make the change permanent–remember that reaching your short-term goal is just the start of your plan. Next, you need to figure out the right diet to maintain your results–that includes which foods you need to eat and how much of them you should consume. You also need to pair nutrition with a rock-solid exercise regime, unless you’re content with being skinny fat.

Otherwise, you’re just going to crash–and burn.

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2 thoughts on “Do Crash Diets Get The Green Light?

  1. Scott Anderson

    Yes, you breifly hit on my biggest concern which is how much of what the crash dieters lost was lean body mass? It is pretty obvious that you could not sustain any kind of workouts on 800 calories/day.

    1. Denis Faye - The Nutrition Nerd Post author

      Scott – The link in there gets into more detail about that:


      You’re right, although sometimes bodybuilders and swimsuit comp folks use low calories to get quick results. I’m not a huge fan, but it can be done, if done only for a short period of time. But yeah, you’re right, they’re going to lose a little muscle with that fat.


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