So you want to lose weight. And you'd like to lose that weight as
quickly and safely as possible. Maybe you've read that a 1200 calorie
diet is the lowest calorie intake you should have, if you are a woman,
to not slow your metabolism. (For men this number is 1500 to 1600
calories.) What do you need to do to get started, will it work, and is
it safe?
1200 calories is not a magical number. It is a suggested
minimum for women because is it difficult to achieve nutritional balance
with less. In addition, most women need at least this number of
calories for adequate energy to keep physiological processes working
even when at rest. That is, you have a need for calories, a measure of
potential energy, for such things as keeping your heart beating and your
lungs working so you can breath. Because these processes are essential
for life, your body will fight to keep them going.
If you fail to provide needed calories, your body senses an urgency to reduce energy expenditure and conserve stored energy (fat) to make it last until food is more readily available. Your metabolism slows down. This survival mechanism comes from thousands of years of evolutionary adaptation to food scarcity and times of starvation.
To avoid having your metabolism slow down, you will want to estimate the rate at which YOUR body burns calories even when at rest. This is called Basal Metabolic Rate (BMR). (Resting metabolic rate or RMR is similar though not exactly the same as BMR, however, the two are often used interchangeably.) Both BMR and RMR can vary widely. For some women, BMR is less than 1200 calories a day but for many women it is likely to be MORE than 1200 calories.
Small, thin, and/or older women will have lower BMR's than younger or heavier women. So you will want to determine your BMR as accurately as possible. This value will be your starting point. Don't go on a low calorie diet with fewer calories than this.
A calorie intake less than your BMR can lower your metabolic rate by 10% or more in as little as 48 hours. To be on the safe side and avoid metabolic slowdown, consider increasing your caloric intake every third day while on a low calorie diet. If you start on a 1200-calorie diet simply raise your caloric intake to say 1500 calories or so every third day (200-300 calories more than YOUR BMR). This will send a message to your body that you are not starving and food is available. You will be less likely to have a metabolic slow down. And, you will have a small break from your low calorie diet as well!
The other thing you will want to keep in mind is the need for extra calories when you exercise. Exercising puts added stress on your system. Remember to take this into account and provide your body with enough calories to cover your exercise cost and BMR. Neglecting to do this could actually lower your metabolism more than might occur simply by not eating enough to meet your BMR needs without exercise.
You might wonder why you should bother exercising at all if you need to eat more to avoid metabolic slowdown. There are several reasons. First of all you may actually increase your basal metabolic rate with regular exercise especially if you do resistance training or weight lifting. Another good reason is that you will be more physically fit. Exercise helps to tone and shape your body as you lose weight. Also, you get to eat more food.
Rest assured that you should lose weight on a lower calorie diet if you are monitoring your caloric intake carefully. You do have a need for calories above and beyond BMR and formal exercise just to get through your day. So you should still have a calorie deficit. This calorie deficit is what will get your body to pull on fat stores for energy rather than slowing down your metabolism to conserve energy.
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If you fail to provide needed calories, your body senses an urgency to reduce energy expenditure and conserve stored energy (fat) to make it last until food is more readily available. Your metabolism slows down. This survival mechanism comes from thousands of years of evolutionary adaptation to food scarcity and times of starvation.
To avoid having your metabolism slow down, you will want to estimate the rate at which YOUR body burns calories even when at rest. This is called Basal Metabolic Rate (BMR). (Resting metabolic rate or RMR is similar though not exactly the same as BMR, however, the two are often used interchangeably.) Both BMR and RMR can vary widely. For some women, BMR is less than 1200 calories a day but for many women it is likely to be MORE than 1200 calories.
Small, thin, and/or older women will have lower BMR's than younger or heavier women. So you will want to determine your BMR as accurately as possible. This value will be your starting point. Don't go on a low calorie diet with fewer calories than this.
A calorie intake less than your BMR can lower your metabolic rate by 10% or more in as little as 48 hours. To be on the safe side and avoid metabolic slowdown, consider increasing your caloric intake every third day while on a low calorie diet. If you start on a 1200-calorie diet simply raise your caloric intake to say 1500 calories or so every third day (200-300 calories more than YOUR BMR). This will send a message to your body that you are not starving and food is available. You will be less likely to have a metabolic slow down. And, you will have a small break from your low calorie diet as well!
The other thing you will want to keep in mind is the need for extra calories when you exercise. Exercising puts added stress on your system. Remember to take this into account and provide your body with enough calories to cover your exercise cost and BMR. Neglecting to do this could actually lower your metabolism more than might occur simply by not eating enough to meet your BMR needs without exercise.
You might wonder why you should bother exercising at all if you need to eat more to avoid metabolic slowdown. There are several reasons. First of all you may actually increase your basal metabolic rate with regular exercise especially if you do resistance training or weight lifting. Another good reason is that you will be more physically fit. Exercise helps to tone and shape your body as you lose weight. Also, you get to eat more food.
Rest assured that you should lose weight on a lower calorie diet if you are monitoring your caloric intake carefully. You do have a need for calories above and beyond BMR and formal exercise just to get through your day. So you should still have a calorie deficit. This calorie deficit is what will get your body to pull on fat stores for energy rather than slowing down your metabolism to conserve energy.