We are told to eat 2500 calories a day. What evidence is this based on?

The suggested caloric intake is based on how much the average person burns per day in order to balance out and maintain calories and weight. Keep in mind that this is an average, the calories you would need to intake varies by age, current/goal weight, and amount of exercise.

Taken from a BMR information website:

Your BMR is the amount of calories you burn at rest. It includes calories burned while sleeping, breathing and pumping blood. It accounts for about 60 to 70 percent of your total calories burned. When dieting, you should never consume fewer calories than your BMR. To estimate your BMR, simply multiply your weight by 10. For a more accurate calculation, use the Harris Benedict Equation. For men: BMR = 66 + (13.7 x your weight in kilograms) + (5 x your height in centimeters) - (6.8 x your age in years). For women: BMR = 655 + (9.6 x your weight in kg) + (1.8 x your height in cm) - (4.7 x your age in years).

The thermic effect of food is the amount of calories you burn while eating. It accounts for about 10 percent of total calories burned.

An excerpt from USDA guidelines:

The calories found in food come from proteins, carbohydrates and fats. Your body uses all three to function. Fats help your body absorb nutrients. Carbohydrates provide energy and protein helps build and repair muscles. The U.S. Department of Agriculture (USDA) recommends that 45 to 65 percent of the calories in a healthy diet should come from carbohydrates, 10 to 35 percent from protein and 20 to 35 percent from fat.

http://en.wikipedia.org/wiki/Harris-Benedict_equat...

The reason the answer is so common is because it is an AVERAGE man's calculation.

Once you get into the differences in people you get different numbers.

You can use other algorithms to calculate BMR as well.

Manual of Nutritional Therapeutics

By David H. Alpers, William F Stenson, Beth Taylor, Dennis M Bier

Harris-Benedict equation.

Harris J, Benedict F. A biometric study of basal metabolism in man. Washington D.C. Carnegie Institute of Washington. 1919.

Try the calculator here:

http://www-users.med.cornell.edu/~spon/picu/calc/b...

This is approximately how many calories the moderately active average person will burn in the course of the day, between body function and whatever they do.

Create a tip from the yoga pros and breathe... more oxygen as part of your cells means more fat will be burned away. Breathing exercises such as those practiced in yoga are a straightforward addition to your daily weight loss regime.

Before the entrée arrives, ask the waitperson to create for you a to-go container so you can package half to save with regard to later.

Make an effort to help make tiny modifications to your diet

decaf coffee is an excellent lower calorie substance

Sit on a yoga ball instead of a chair to work your current core.

This based on about how many calories the average male or female will burn in a day. Eating as many as you burn will keep your weight fairly balanced.