Maybe I’m just picking my favorite answer out of the bunch, but I like how this sounds. Before reading all of these answers, the idea crossed my mind that “starvation mode” is the default, and high calorie burning is simply the result of eating wayyyyy too many calories in a day. Does anyone really need to eat three square meals? Honestly I can eat a couple slices of pizza and pop a multivitamin and I’ll feel fine. So that makes me wonder, how exactly do I know that I’m in the state referred to by Blake? Can someone give me a surefire test? Will I be unable to walk in a straight line or recite the alphabet backwards? Will simple brain teasers be too much thinking for me?
You are just picking your favorite answer, starvation is definitely about calories.
Think of the human body as an engine, engines require a constant supply of energy to run. If you remove an engine’s fuel supply, it’ll very quickly sputter out and cease.
In the case of the human engine, the things that eventually shut down are the heart, brain and other things that need constant energy to survive. When those things shut down, you die.
If you consume less than you burn, every single day, then over enough time you die, period.
I don’t thin you should view starvation “mode” like some sort of setting on a T-1000 that is activated by flipping a switch. If you’re in sustained fat loss you are technically starving. What most people who talk about dieting and weight loss are talking about when they talk about “starvation mode” is when there is a noticeable reduction in metabolic rate due to a dramatic reduction in caloric intake. This is a physiological response to starvation, and is done to hold on as best as the body can. I believe there was a study done in the 1950s that showed 40% reduction in metabolic rate after a 50% reduction in caloric intake, over a six month period.
A couple slices (2) of pizza is going to top out at around 600 calories. If you eat nothing but that every day for a long enough period of time, you’ll suffer serious loss of body weight and die. Let me make something very clear to you: you are not special, you do not posses any sort of super human physiology. If you’re truly consuming less than you burn every single day, over time you’ll lose weight. If it is a dramatic deficit then you’ll probably notice some of the effects that Blake mentioned upthread, and you’ll eventually suffer serious health problems. If you obstinately kept consuming less than you burned, you’d eventually die, period.
If you’re wondering if you’re eating a dangerously low amount of calories, you’ll find out in the gym. As part of your not being superhuman, which I referenced above, you’ll notice that you are not able to exercise as well as before. If you’re used to running at a certain intensity for a certain period of time, if you had subjected your body to such a drastic reduction in calories that your metabolic rate had significantly slowed, then you would not be able to do the same things you normally do at the gym.
You’ll also, if you lift weights, notice a dramatic reduction in lifting power. As someone who has been a serious lifter for my entire life, I can tell you for sure that anytime you’re losing weight it’s very difficult if not impossible to not have some loss in lifting ability at least during the cutting process. If you have no trouble at all while lifting, or especially if you’re able to increase the amount you’re lifting over time, you’re not eating less than you burn you cannot meaningfully increase muscle mass or strength if you’re operating at a caloric deficit.
The biology/biochemistry of starvation is quite fascinating. First, your body “burns” the glucagon reserves in your liver. Once that’s depleted, and you are truly starving, your body begins metabolizing amino acids and proteins; your body mass decreases as you literally start “eating” your own muscles.
Of course, this is not sustainable, so after about two or three days, you begin metabolizing fat and adipose tissue, resulting in the formation of “ketone bodies,” small organic molecules which can feed into the Krebs (or maybe it was citric acid) cycle.
For a surefire test of whether you are in starvation mode, go to the drugstore and buy some “Keto Strips,” and look at the amount of ketone bodies in your urine. No ketosis, no starvation
Ketosis and starvation mode are different things. You metabolism can adjust to changes in intake (and any such change is what the OP means by “starvation mode”) without switching over to ketosis.
My apologies to all. I was referring to the biological meaning of the term “starvation”.
Perhaps what you are talking about might better be called “low caloric intake?”
If you are undergoing prolonged weight loss, which you would see if you were intentionally operating at a ~400 calorie deficit per day, your body would be in ketosis. Ketones are released when the body is removing stored energy from fat cells, so any form of weight loss that is resulting in using up your body’s fat stores will result in ketosis. (My understanding is ketones are bad to have around in your system, too, but that the benefits of long term weight reduction outweigh this.)
Your body generally will not go into ketosis if it is consuming more calories than are needed, because your body doesn’t tend to cut into its stores when it has a surplus, but instead starts packing more in.
This is why I said upthread that all weight loss is starvation, precisely because you cannot make your body give up energy stored in fat cells until you’ve created a caloric deficit. A caloric deficit that never ends ultimately terminates in death (obviously that would never happen to a person casually dieting in a first world country, but assume that you always operated at a small deficit, with your caloric intake slowly going down to maintain that deficit even as your decreased weight meant you burned fewer calories, eventually you’d reach a critical point and die from this.)
What the OP is primarily concerned with is this concept you see a lot amongst dieters: “decreased metabolism.” If you’ve read many diet web sites you’ll see that most of the caution against extremely low calorie diets because they warn that it can lower your metabolic rate and actually decrease your weight loss. This is true in a very general sense but there’s nothing magical about it, 600 calories a day will always be insufficient to maintain weight regardless of the fact that such a diet will cause you to operate at a lower level of energy consumption.
So I guess to come sum things up… there are two different types of notable starvation mode. Starvation in the sense of not eating enough and wasting away into nothing which happens when you run out of fat, glycose blah blah and your body eats everything in a desperate attempt to gain energy. Alright. Then there’s the “starvation mode” that all of these stupid web sites refer to which is more or less just a metabolic roller coaster that happens if I were to eat a lot after not eating that much? Does that cover everything?
And yet, someone on the Atkins diet can eat steak and lobster, and still be in a state of ketosis due to lipid metabolism.
Wierd, huh?
No, because the Atkins diet, if it is working, still results in a caloric deficit. The thing with Atkins is it’s supposed to stimulate entering ketosis faster than you would enter it normally.
Steak and lobster, by the way, actually aren’t very high in calories. A half a sleeve of Oreos has more calories in it than 20 oz porterhouse.
It seems to me that the “starvation mode” thing is one of many nutritional myths that get passed around to the point that they become established truths, despite the lack of actual evidence. It does appear to be true that people who are literally starving become listless and generally inactive in order to conserve energy, but we are talking about famine victims here, a level of hunger way beyond that experienced by westerners who are merely on a diet, or eating irregularly, as in the case of the OP.
For people with healthy reserves of body fat, it takes quite some time for that reaction to happen. It doesn’t happen just because you’re hungry. Instead, fat and other tissue gets converted to energy, i.e. you lose weight. Starvation mode doesn’t happen unless you eat virtually nothing for several days.
http://nutritiondiva.quickanddirtytips.com/metabolism-myths.aspx (popular article, but has some academic cites)