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How Many Calories Should I Eat – Weight Science

MealPro , On June 20, 2016


How many calories should I eat? Seriously though, how much?

There are two fundamental principles to food consumption in ‘Nutritional Science’. The BMR Formula and The Harris Benedict Equation:

1. The BMR Formula is how many calories you would burn if you slept all day. It uses the variables of height, weight, age, and gender to calculate the Basal Metabolic Rate (BMR). This is more accurate than calculating calorie needs based on body weight alone. The only factor it omits is lean body mass and thus the ratio of muscle-to-fat a body has. Remember, leaner bodies need more calories than less lean ones. Therefore, this equation will be very accurate in all but the very muscular (will underestimate calorie needs) and the very fat (will over-estimate calorie needs). Women and men have two different formulas:

  • Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age)
  • Men: BMR = 66 + (6.23 x weight in pounds ) + (12.7 x height in inches) – (6.8 x age)

2. The Harris Benedict Equation is a formula that uses your BMR and then applies an activity factor to determine your total daily energy expenditure (calories). The only factor omitted by the Harris Benedict Equation is lean body mass. Remember, leaner bodies need more calories than less lean ones. Therefore, this equation will be very accurate in all but the very muscular (will underestimate calorie needs) and the very fat (will over-estimate calorie needs). Here are the activity levels:

  • Little/no exercise: Calorie-Calculation = BMR x 1.2
  • Light exercise/sports 1-3 days/week: Calorie- Calculation = BMR x 1.375
  • Moderate exercise/sports 3-5 days/week: Calorie-Calculation = BMR x 1.55
  • Hard exercise/sports 6-7 days/week: Calorie-Calculation = BMR x 1.725
  • Very hard exercise/sports & physical job: Calorie-Calculation = BMR x 1.9

The Diet Analysis Calculator combines the BMR Formula and Harris Benedict Equation to find your calorie need. You can cross reference with the above formulas to make sure your number is correct. Give it a try:

If you want to gain weight you need to consume more calories than you burn. One pound of body weight is roughly equivalent to 3500 calories, so eating an extra 500 calories per day will cause you to gain one pound a week.

For optimum health, if you increase your calories to gain weight then (health permitting) gradually increase your level of physical exercise in order to maintain or increase your lean body mass. The benefits of exercise on physical and mental health are well documented and shouldn’t be ignored.

If you want to lose weight you need to consume fewer calories than you burn. There are approximately 3500 calories in a pound of stored body fat. So, if you create a 3500-calorie deficit through diet, exercise or a combination of both, you will lose one pound of body weight. (On average 75% of this is fat, 25% lean tissue) If you create a 7000 calorie deficit you will lose two pounds and so on. The calorie deficit can be achieved either by calorie-restriction alone or by a combination of fewer calories in (diet) and more calories out (exercise). This combination of diet and exercise is best for lasting weight loss. Indeed, sustained weight loss is difficult or impossible without increased regular exercise. Cardiovascular exercise at 60% to 75% of your max heart rate is ideal target heart rate zone for weight loss, in this zone your body breaks down fat to use as energy.

If you want to lose fat, a useful guideline for lowering your calorie intake is to reduce your calories by at least 500, but not more than 1000 below your maintenance level. For people with only a small amount of weight to lose, 1000 calories will be too much of a deficit. As a guide to minimum calorie intake, the American College of Sports Medicine (ACSM) recommends that calorie levels never drop below 1200 calories per day for women or 1800 calories per day for men. Even these calorie levels are quite low.

An alternative way of calculating a safe minimum calorie-intake level is by reference to your body weight or current body weight. Reducing calories by 15-20% below your daily calorie maintenance needs is a useful start. You may increase this depending on your weight loss goals.

Nutrition Aspect:

So, how many calories should I eat?

Once you know your goal and understand the science, the next step is to get great nutrition. The challenge is many eateries do not align with your goal and grocery shopping can be a time costly endeavor. MealPro is the only nutrition company to factor in your BMR and Harris Benedict Equation when building your meal bundle. With minimal effort, you can have a meal delivered to your door that fit your needs. can greatly simplify the process.


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