I lifted this directly and in its entirety from Coach Deans response in this thread:www.sparkpeople.com/myspark/messageboard.a
I would agree that "starvation mode" is a concept that gets overused and misunderstood very often and easily. Eating too little will not cause you to stop losing weight or gain weight over the long term. It can cause that effect in the short term, if the calorie deficit is not too large, because your body does have mechanisms for slowing down your metabolism to conserve energy, in order to cope with short-term variations or shortages in food supply.
Basically, your body is all about "homeostasis," or maintaining its internal conditions within a small range. This is obvious when you look at something like blood pressure or body temperature--your body has all kinds of little "tricks" it can use to maintain its core temperature, for example, within a narrow range. It can sweat when it gets hot, shiver when it gets cold, divert blood flow away from or towards certain critical areas, etc.
The same is true about energy balance--energy in versus energy out. When there isn't enough energy coming in to meet current needs, there are many tricks your body has for reducing your energy needs to more closely match what's available. From the outside, it can look like your weight loss slows down or even stops for a little while, but that's not your body's "goal," and it's not really trying to "conserve fat." It's simply doing what it can to reduce energy expenditure by slowing down or shutting off certain non-essential operations (like growing and repairing hair and nails) and shifting where it gets the fuel it uses for immediate needs.
Which of these tricks it will use depends on how big the shortage is, how long it's been going on, and other factors, including your own genetic dispositions. And what effect all this has on your weight also depends on these factors. Which means there isn't any simple way to predict in advance what you should expect if you reduce calories or increase exercise by X amount instead of Y amount.
I think that, if there's a general policy you can follow to protect against "starvation mode", it would be that you should not eat less than it would take to maintain good health and nutrition if you were already at your goal weight. Or, to put it another way, you should eat and exercise as if you're already at your goal weight, and let your body take care of eliminating any excess fat you have right now. As always with general rules, there are exceptions--people with some obesity-related health problems, and people who are morbidly obese to the point that their health is in immediate jeopardy, may need to do things differently, as suggested by their doctor.
Since there is so much confusion about the idea of starvation mode here on the message boards, I've been working on a little quiz people can use to sort out some of the common misconceptions. Here are some of the common statements you'll see/hear about starvation mode, and an explanation of whether they are true or false, and why:
1. The larger the deficit between the number of calories you eat and the number of calories you need to maintain a normal weight, the faster your body will take fat out of storage and burn it as energy.
Excessive calorie restriction actually slows down your metabolic rate (the calories you use just to keep all your necessary bodily functions operating)—often by as much as 40%, according to several studies. This can amount to as much as 400-800 fewer calories burned per day, which is definitely enough to make your weight loss go slower than your calorie deficit numbers say it should. But this drop in metabolic rate is not enough to stop weight loss or fat loss completely (otherwise it would be impossible for people to starve). The real problem is that it can and does change where the lost weight comes from. While moderate calorie restriction allows your body to get most of the additional energy it needs from your stored fat, severe calorie restriction forces it to use the energy stored in your muscles and organs to a much greater degree, which can be debilitating and even fatal in cases of true starvation. Since your muscle and lean organ tissues are the real calorie burners in your body, the more of it you lose, the less you can eat without gaining weight and the harder it becomes to lose fat. This also explains why people who lose weight with semi-starvation diets almost inevitably regain all that weight and more when they return to normal eating levels—and it doesn’t come back as muscle or organ tissue, it comes back as fat.
2. If you consistently eat less than 1200 calories per day (1500 for men), your body will go into starvation mode.
Although there are important reasons why people shouldn’t go below these minimum calorie intake levels (see Question 6 below), there is no single level of calorie intake that determines when people will shift into “starvation mode.” What determines this is the difference between your calorie intake and your needs, which varies for everyone depending on factors like size, age, gender, health factors, and activity level. Also, your individual genetics play a large role in how quickly and how strongly your body responds to extreme calorie deprivation. In most cases, a starvation-level diet is one that persistently provides less than 50% of the energy you would need to maintain your ideal weight at your normal activity level. That could be quite a bit more or less than 1200 calories, depending on individual factors, and it will normally take more than an occasional day of going too low on calories to cause problems.
3. Less overweight individuals will lose a larger percentage of lean muscle and organ tissue and less fat than obese individuals, when they restrict calorie intake too severely.
Evidence indicates that people with a Body Mass Index of 30 or less will lose their lean body mass more quickly and easily than people with a BMI over 30 (obese). To a large extent, this is just common sense—people with less fat to lose will lose more of their weight from other sources if they force the issue through excessive calorie restriction. But there also may be biological mechanisms that cause people with less total body fat to rely more on protein stored as lean tissue during excessive calorie deprivation. In any case, it’s clear that the less weight you have to lose, the more important it is to avoid excessive calorie restriction and rapid weight loss.
4. Regular strength training and cardio exercise can prevent the excessive loss of lean body tissue, even when calories are restricted too severely.
It’s true that strength training and other exercise will minimize the loss of lean muscle and maximize the loss of body fat, when individuals restrict calorie intake moderately. The combination of moderate calorie restriction (enough to lose one half to 2 pounds per week, depending on your starting weight) and regular strength training can reduce lean muscle loss from 25% of total weight lost (normal, when exercise is not included) to 3-5%. However, this muscle protecting effect of exercise is mostly lost when calorie deficits become too extreme, because there are not enough resources available to support muscle recovery or, eventually, to fuel the necessary exercise activity.
5. It’s OK to have a very large deficit between calories in and calories out, as long as most of the deficit comes from lots of extra cardio exercise and not from eating too little.
Since the trigger for starvation mode problems is having too much of a difference between what you need and what you take in, it really doesn’t matter how that deficit gets created. In fact, excessive cardio exercise can actually increase the problem of breaking down muscle tissue to obtain needed energy, because your body can’t use much fat as energy when you are working out at higher intensity levels. It must rely mainly on glucose, and if your diet doesn’t provide enough energy to fuel this extra exercise, or replenish your muscle glycogen fuel tanks between bouts of exercise, your body has no choice but to start breaking down the protein in your muscles and organs so it can be converted into glucose to fuel your activity.
6. Which of the following is a likely negative effect of going below 1200 calories per day, for women, or 1500 for men?
“ You probably will not get the right combination of vitamins, minerals, other micronutrients, fiber, and macronutrients (carbs, fats, protein) you need to maintain good health and adequate energy levels for your daily activity.
“ You may begin to suffer significant psychological and physical problems, including obsession with food and eating, agitation, stress-related hormonal imbalances, sleep and mood disturbances, difficulties with concentration and attention, and fatigue.
“ You may compromise the functioning of your immune system, making it more likely that you’ll catch colds and flus, be more susceptible to long-term problems associated with inflammatory processes (like atherosclerosis), and experience other avoidable health problems.
“ All of the above.
All OF THE ABOVE.
Although your individual trigger point for starvation mode problems may be above or below SP’s minimum recommended calorie intake level, there’s not much doubt that just about everyone will have problems meeting their nutritional needs if they let their calorie intake drop below these levels consistently. Even at these minimum levels it can be hard to maintain good nutrition without being very strict about limiting empty calories and making well-informed food choices. And remember—“healthy” means more than just keeping your carbs, fat and protein within recommended ranges for weight loss. There are many micronutrients necessary for optimal health and well-being that aren’t shown on food labels—like all the phytochemicals, bioflavonoids, catechins, and other substances found in specific fruits and vegetables, that enhance immunity, defend against the negative effects of stress, promote emotional well being—and keep your body firing on all cylinders so you can efficiently burn that fat you want to lose.
7. The best dieting strategy for avoiding starvation mode problems, maximizing your fat loss, and keeping the weight off permanently is to eat and exercise as if you’ve already reached your goal weight and are trying to maintain that weight with a healthy lifestyle.
If you want to be a success in the permanent weight loss game, this is by far the best strategy to follow. Figure out how much a person your age, gender, and height, who weighs what you want to weigh, would need to eat in order to maintain that weight if s/he is doing the amount of exercise and daily activity you think you can live with on a long term basis. Then start doing all that—right now. Your calculation should include your BMR at your goal weight, plus about 20% of that for regular daily activity, plus whatever additional calories you expect to burn with exercise. You’ll probably need to experiment a little to get the numbers dialed in right for you.
There are a few possible complications that some people may run into with this simple formula. For example, if you have a lot of weight to lose (say, 75 pounds or more), cutting your calorie intake down to the amount you’d need for maintenance at your goal weight may make your calorie deficit at the beginning too large. Ideally, your calorie deficit should not exceed 1000 calories per day by very much, if you’re not under medical supervision, and the difference in calories needed to maintain your goal weight versus your current weight may be more than that. If so, you may need to pick an intermediate goal weight that is higher your final goal, and use that to do your math until you’ve lost some weight.
Likewise, if you’re already very close to your goal weight, you may need to eat a little less than your estimated maintenance level, just to make something happen. There’s just not much difference in the numbers when the difference between current and goal weight is only 5 pounds. But don’t make the mistake of thinking you can try to lose 2 pounds per week. Think in terms of aiming for a deficit of about 250 calories per day.
If you’re the impatient sort, your biggest challenge here may be finding the patience to settle for whatever rate of weight loss this approach lets you achieve. But in the long run, you’ll be glad you did. Honest.
Hope this helps.
Start by doing what is necessary, then do what is possible and suddenly you will be doing the impossible -- St Francis of Assisi
Rock 'n' Roll Dublin Half Marathon, Dublin, Ireland, 8/5/2013 ie.competitor.com/dublin/