So let's start by examining the whole "starvation mode" idea that you see all the time in articles about dieting. I picked this one to start with because I'm now tracking my food on My Fitness Pal and the number of people there screaming "starvation mode" is about 10x higher than most of the other weight loss boards I go to. They annoy the heck out of me, so I want to "answer" them in a permanent way vs. just arguing with them over and over on the boards there.
So what is the Starvation Mode Myth? It goes like this:
"If you don't eat enough, you won't lose weight!"
Okay, so all I have to do to lose weight is ... eat more food! Wow, isn't that awesome? If I stall out at 800 calories, I'll just go up to 1000. And if I stall at 1000, I'll go to 1200. If that doesn't work, how about 1500? 1800? 2200? Oh wait, when I ate 2200 calories, I weighed 223 pounds. Okay, that's not going to work.
But what if I just don't go below the magic "1200" that "everyone" says "no one" should go below? That must be what they mean by "starvation mode," right? If I stay at 1200, I will lose weight but if I go below that, I won't.
The problem with this idea is that, if it were true, no one would die from starvation and obviously people do. Clearly, even if you eat what is obviously too few calories to be healthy, such as an anorexic does, you will continue to lose weight.
So where did this idea -- that not eating enough calories makes you not lose weight -- come from?
It started with the famous Minnesota starvation study. Some normal-weighted men agreed to live on a compound where their exercise and diet was strictly controlled. For portions of the study, they were on a "starvation diet" which is defined as 50% of the calories your body needs to function.
For me, these days, that's about 750-850 calories a day. So I was on a starvation diet up for the first four months after my surgery. Yet I lost weight just fine during that period -- better than fine, really. Most of the people on The Biggest Loser are also on starvation diets, from what I can tell. They may eat a lot more than I do but they also exercise strenuously 6-8 hours a day. So they are often below 50% of their calorie expenditure for the day. They seem to lose just fine too.
How can this be?!
The answer lies in what actually happened to the Minnesota guys when they were on their starvation diets.
Like most of us on a diet, their metabolisms did slow down. In fact, after they'd been on this diet for a while -- we're talking months, not days here -- their body fat percentage got to a point below what is considered minimal to live on (about 5% for a guy, 6% for a gal). At this point, their metabolism had slowed down as much as 40%. But -- and this is the important point for those of us on a diet -- they continued to lose weight. Even with that big of a slow down in their BMR (Basal Metabolic Rate), they were still operating at a great enough calorie deficit to lose.
If this is true with a 40% slow down, it's even more true when the slow down is somewhere in the 14 - 22% range, which is more where if falls with normal dieting.
WARNING MATH CONTENT AHEAD:
Take an individual who needs 2,000 calories per day to maintain their current weight. Assuming calorie expenditure remains the same, they will lose (approximately) as follows:
|2,000||0 pound||0 pound|
|1,500||1 pound||1 pound|
|1,000||2 pounds||2 pound|
|500||3 pounds||2¼ to 2½ pounds|
As you can see from the table, once you go below a certain calorie level, you aren't getting the weight loss you'd expect. This is because your BMR will go down more if you eat only 500 calories compared to eating 1500. But, as you can see, you are still losing more than if you were eating 1000 calories.
This is a lot different than the "no" weight loss that the "starvation mode" myth touts.
The other important point to note about this study is that it was performed on normal-weighted men. When starvation studies have been done on the obese, they find that the impact of the starvation diet is much less. Our bodies have fat stores designed to get us through a famine (i.e., a diet) and when we have a famine (i.e., a diet), those fat stores get used. The drastic slowdown of the metabolism doesn't happen until those fat stores are largely gone -- which takes a lot longer for the obese than for those who only have to lose 10-25 pounds.
So why are we told not to go under 1200 calories a day, unless under a doctor's supervision?
Mostly because, the more you reduce your intake, the harder it is to get the nutritients you need from food. If you are on a very low calorie diet (as I am), you need to see your doctor(s) regularly, get labs done regularly, etc. Not to mention, vitamin supplementation is a must. Doing what I'm doing on your own can be dangerous, as you may not know or noticed the signs of a vitamin or mineral deficiency. Don't forget: some vitamin deficiencies can kill you!
Another reason not to go below a certain calorie expenditure is that human beings are not machines and, unlike the guys in the Minnesota study, we aren't living on a compound with our activity and food strictly controlled. As a result, when we reduce our calories substantially, there is a tendency to subconsciously (or even consciously) reduce our calorie expenditure. Combine this with our tendency to under-report what we eat and over-report our exercise, and you can see where we can get into trouble.
As an example, one Saturday I did a killer two hour workout. After which, I came home and took a three hour nap! Obviously my calorie expenditure that day was lower than if I hadn't taken the nap.
Now, I still lost weight that week. But if I was only eating 500 calories for months at time, I doubt I'd be able to have done that workout to begin with -- I'd still be doing the 30 min. low intensity workouts that I started with. Plus, I might also be taking naps a lot more than once in a while. Both of which would have impacted my weight loss because they would have decreased my calorie expenditure.
Eating more over time has allowed me to exercise more so that, as a result, my rate of weight loss hasn't gone down as much as it could have as my calories have gone up. Plus I'm happy because I'm fitter and healthier.
In the end, it's important to consume enough calories that you have the energy to perform the daily activities you want to and to keep your body healthy. Otherwise, it's self-defeating. After all, the point of losing weight is to be healthier and to get our lives back. It's not to starve ourselves to the point of malnutrition and have so little energy we can't go out and do fun things.
If you want to learn more about starvation mode and read more details about the studies I alluded to, here are some good articles on it:
Are You In Starvation Mode or Starving For Truth? (some typos but the best summary article I've seen)
The Starvation Myth (where I got my table from)
The Truth about "Starvation Mode" (lots of research is discussed)
And here's an article from the other side... Tom Venuto is a big proponent of Starvation Mode and avoiding it. Yet even though the tone of his article makes it sounds like he disagrees 100% with the articles above, about 90% of what he says is exactly the same:
Is starvation mode a myth?- No! It's very real and here is the proof