But if i also take vitamins will my metabolisim still slow down?
Vitamins should not affect your metabolism. Vitamins have no calories.
Why does a very low calorie intake slow down weight loss?
Quite simply, your body goes into 'starvation mode'. This mechanism, which is thought to have evolved as a defense against starvation, means the body becomes super efficient at making the most of the calories it does get from food and drink. The main way it does this is to protect its fat stores and instead use lean tissue or muscle to provide it with some of the calories it needs to keep functioning. This directly leads to a loss of muscle, which in turn lowers metabolic rate so that the body needs fewer calories to keep ticking over and weight loss slows down. Of course, this is the perfect solution if you're in a famine situation. But if you're trying to lose weight, it's going to do little to help you shift those unwanted pounds.
So how many calories should I have to prevent starvation mode?
Unfortunately, there's no single answer to this question. As everyone's metabolism varies in the first place, so too will the point when the body starts to use muscle to provide it with calories in a 'famine-type' situation.
As a general rule though, most nutrition experts recommend never going below 1,000-1,200 calories a day if you're dieting on your own.
What's the link between muscle and metabolism?
The metabolic rate - the rate at which the body burns calories - is partly determined by the amount of muscle we have. In general, the more muscle we have, the higher our metabolic rate; the less muscle we have, the lower our metabolic rate. This explains why men, who have a high proportion of muscle, have a faster metabolism than women, and why a 20-year-old has a higher metabolism than a 70-year-old - again, they have more muscle.
Ultimately, muscle burns a lot more calories than fat so when we lose muscle, our metabolic rate drops and we burn fewer calories. In fact, research shows that the body loses a proportionately high amount of muscle with a very low calorie intake and this may considerably suppress metabolism by up to 45 percent.
This explains why it's crucial to do as much as you can to protect your metabolic rate, especially when you're dieting. And this means dieting sensibly with a suitable, rather than a very low calorie intake so that you lose fat rather than muscle.
Why are you on a 1200 calorie a day diet? Are you trying to lose weight? Maintain your weight?
Who is supervising your diet? A doctor? A nutritionist? Have you tried to discuss your questions with them?
What kind of exercise do you do? 700 calories is a lot to burn off exercising in one day--are you sure you aren't overdoing the exercise?
Concentrate on getting 1200 calories a day on a sensible, well balanced diet. Don't worry about replacing the calories you are burning off exercising unless you start losing weight too quickly. If you are exercising a good deal each day, you should discuss this with your doctor, or with the health professional who is supervising your diet. They might suggest increasing your total calorie intake, perhaps to 1500 calories a day to balance out what you burn off exercising. If your goal is to lose weight, you are better off doing that gradually and slowly, aiming for a weight loss of no more than 2 lbs a week. And you should do this under a doctor's supervision.