According to the AMA the body needs 1200 calories per day to survive well long term, so that could be a maintenance goal, probably 1200 to 1500 women, 1500 to 1800 men depending on exercise level.
-The heart needs 12% of the calories (144 cals)
-The kidney needs 12% of the calories (144 cals)
-The Liver needs 23% of the calories (276 cals)
-The brain needs 23% of the calories (276 cals)
-The skeletal muscle needs 30% of the calories (360 cals)
While in the losing stage of the first 6 months or so I would think 800 to 1000 calories is fine. I don't think below 800 is good long term, as your body goes into starvation mode if the calorie count is too low for too long.
Here is a guide for finding your basal metabolism rate that might help.
Here is how you can figure your BMR and your caloric needs so that you can stay within 500-1000 calories of your needs. This is the most effective method of losing body fat and not losing water and muscle.
Imperial(US) BMR Formula
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
Metric (Canada) BMR Formula
Women: BMR = 655 + ( 9.6 x weight in kilos ) + ( 1.8 x height in cm ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 13.7 x weight in kilos ) + ( 5 x height in cm ) - ( 6.8 x age in years )
This will calculate what you require even if you were to sit on your butt all day or sleeping most of the day. Because this is roughly how many calories your body will burn as a living, breathing, eating, heart-beating, digesting etc.. being. This does not include your daily activities. It is really easy to not eat enough, so you need to factor in your activity levels.
Harris Benedict Formula To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:
- If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
- If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
- If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
- If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
- If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9
The calorie deficit should be achieved by a combination of fewer calories in (diet) and more calories out (exercise). This combination of diet and exercise is simply the best for lasting fat loss.
If you want to lose fat, a useful guideline for lowering your calorie intake is to reduce your calories by at least 500 below your maintenance level. One pound of fat = 3500 calories. That is why 1-2lbs per week is the best rate of fat loss. Anything faster long term could mean you are losing muscle mass and losing water. You want to lose FAT without doing damage to your body.
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