Because the response to my blog post on fast versus slow weight loss was so strong, I decided to review a recent study about the long-term results of crash dieting.
More specifically, the study investigated what happens to appetite hormones after 10 weeks of dieting… one year later.
The Crash Diet Study
This year-long study involved 50 people with Body Mass Indexes (BMI) of between 27 and 40 (this is considered overweight or obese), who went on an extreme low-calorie diet for 10 weeks.
What’s an extreme low calorie diet?
In this case subjects were limited to between 500-550 calories a day. Since the average weight of the subjects was 209 pounds, this equates to around a third of their basal metabolic rate.
In other words, to live without moving at all, these people would burn about 1700 calories a day on average.
Without a doubt, these people were living pretty hungry for 10 weeks!
What this means is that on average the subjects were burning at least 1200 more calories per day than they were consuming.
Since fat has 3600 calories per pound, you would figure they should lose a pound of fat every three days. So at the end of 10 weeks (70 days) they should lose just over 23 pounds or 11% body weight in fat.
During the 10-week crash diet, subjects lost on average 20.7 pounds of fat and 9 pounds of lean muscle… but the results didn’t last over the next year.
As the year progressed, they slowly gained back half the weight they had lost. At first reading, this sounds pretty good. They lost a fair bit of weight in a short period, and then a year later, they were still ahead of the game.
The Short Term Hormonal Effects
The problem is what happened to their hormones that regulate appetite, hunger, and satiety… like leptin, ghrelin, peptide YY, and others.
After 10 weeks of starvation the volunteers had less leptin, peptide YY, and cholecystokinin, as well as more ghrelin and gastric inhibitory polypeptide.
As a result, the volunteers felt hungrier after the study than they did before it started. And this was not psychological, it was hormonal.
You might say this kind of makes sense because the subjects were just getting off of a crash diet and hunger is nature’s way of saying, “Hey, it’s time to eat something.”
It figures that crash dieting messes up appetite regulatory hormones for a short period, but until now, nobody had looked at the long-term effects.
The Long Term Hormonal Effects
Here is where it gets interesting and a little disturbing.
When the researchers looked at the long-term hormonal effects one whole year after dieting, the volunteers still suffered the same hormonal consequences as they had right after the diet.
And they still felt more hunger than before the diet took place.
Again it was not psychological hunger, it was the real thing.
Think about this again. A full year after dieting, the subjects still felt hungrier.
So it’s no surprise that most crash dieters regain their lost weight and eventually end up heavier than when they started.
The Take Home
There is a limit to how low a low calorie diet should go. There is still a debate on the magic number, but I would not recommend going any more than a couple hundred calories lower than your basal metabolic rate over a prolonged period of time.
Luckily, with RealDose Weight Loss Formula No.1 you can double your results even on a modest calorie restriction regimen.
And another thing to note is that the study tracked just one diet over one year. It is common for chronic dieters to do multiple crash diets in a year. If the hormonal effects from just one diet lasted for a year, imagine the hormonal effects of multiple crash diets.
My advice is to pick a plan, like our Fat Loss Fast Start Program or any other healthy long-term plan, and stick to it. And don’t fall for the tempting illusion of the crash diet.
Dr. Steven Sisskind, M.D.
Steve Sisskind, M.D.
Hi, I'm Dr. Steve Sisskind, Chief Medical Officer & Founder at RealDose Nutrition.
As a young physician, I struggled because my patients came to me with serious health issues, but I didn't have the right tools to help them. Medical school taught me how to put "band aids" on their symptoms with drugs and surgery, but not how to address the root causes of their problems.
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Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A, Proietto J.
Long-term Persistence of Hormonal Adaptations to Weight Loss. N Engl J Med. 2011 Oct 27; 365 (17): 1597-604.