The total number of calories a person needs each day depends on a number of factors, including the person’s age, sex, height, weight and level of physical activity.

The number of calories you habitually consume each day determines whether you lose, maintain or gain weight.

How many calories a day should you consume?

The 2015 Dietary Guidelines for Americans estimates the number of calories needed to maintain caloric balance according to sex, age group and three different levels of physical activity: sedentary, moderately active and active.

Estimates range from 1,600-2,400 calories per day for adult women and 2,000-3,000 calories per day for adult men. Within each sex and age category, the low end of the range is for sedentary individuals; the high end of the range is for active individuals. Due to the reductions in basal metabolic rate that occur with aging, caloric needs generally decrease for adults as they age.

The physical activity categories are: sedentary, moderately active, active

Males

• Estimated calorie needs for males in their 20s: 2,400; 2,800; 3,000

• Estimated calorie needs for males in their 30s: 2,400; 2,600; 2,800/3,000

• Estimated calorie needs for males in their 40s: 2,200/2,400; 2,400/2,600; 2,800

• Estimated calorie needs for males in their 50s: 2,200; 2,400; 2,600/2,800

• Estimated calorie needs for males in their 60s: 2,000; 2,200/2,400; 2,600

• Estimated calorie needs for males in their 70s and above: 2,000; 2,200; 2,400/2,600

Females

• Estimated calorie needs for females in their 20s: 1,800/2,000; 2,000/2,200; 2,400

• Estimated calorie needs for females in their 30s: 1,800; 2,000; 2,200

• Estimated calorie needs for females in their 40s: 1,800; 2,000; 2,200

• Estimated calorie needs for females in their 50s: 1,600; 1,800; 2,200

• Estimated calorie needs for females in their 60s: 1,600; 1,800; 2,000

• Estimated calorie needs for females in their 70s and above: 1,600; 1,800; 2,000

For adults, the reference man is 5 feet 10 inches tall and weighs 154 pounds. The reference woman is 5 feet 4 inches tall and weighs 126 pounds. If those seem like low weights, that’s because by today’s standards they are.

The average American man is just over 5 feet 9 inches tall and weighs 195.7 pounds, according to the CDC. The average male’s waist circumference is 40 inches.

By comparison, the average American woman is just under 5 feet 4 inches tall weighs 168.5 pounds. Her average waist circumference is 38.1 inches.

Americans have gotten a lot bigger in recent decades. In 1960, the average man weighed 166.3 pounds; the average woman weighed 140 pounds. The growth in waist size is particularly troubling.

Waist size is a good measure for the risk for certain diseases, including stroke, heart disease and type 2 diabetes. Studies have found that overweight people with large waists — more than 35 inches for women and more than 40 inches for men — are at greater risk of risk of developing type 2 diabetes and are more likely to have a heart attack.

We can change these lifestyle diseases by changing our lifestyle. One of the best changes would be limiting our excess calorie consumption.

The average American consumes more than 3,600 calories daily, according to The Food and Agriculture Organization of the United Nations, which is a 24% increase from 1961, when the average was just 2,880 calories. For some healthy adults, who want to maintain their weight, that’s nearly double the daily recommended requirement.

The problem is that, on average, people underestimate their caloric consumption by about 500 calories. So, if you think you’re eating 2,000 calories per day, you may be getting about 2,500. That adds up to plenty of unwanted weight gain by the end of the year.

If you want to maintain your weight, you need to eat according to your true physical activity level. If you want to lose weight, you’ll need to eat even less, and you’ll also need to perform weight training.

But that’s another story for another day. Feel free to ask me about it.