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All About Calories and How to Burn Them

You know you want to burn them, but do you know how they work?

Woman Jumping Rope
Liam Norris / Getty

Anatomy of a calorie:

The scientific definition: 1 calorie (the kind we measure in food, aka a large calorie) is the amount of energy it would take to raise the temperature of 1kg of water by 1°C.

Almost everything you consume has a calorie count, or the amount of energy stored in its chemical bonds. That energy is released in digestion and stored as other molecules like glucose or fat, so your body can grab it for fuel when needed.

Calorie breakdown:

  • 10% of the calories you eat are used to digest food
  • 20% are used to power physical activity, like lifting weights or walking
  • 70% are used to support the basic functions of your organs and tissues (aka resting metabolic rate)

3 truths about calories

1. Quality counts

Pay more attention to the type of calories than the amount. “Feeding your body real food can help boost your metabolism,” explains Marjorie Cohn, M.S., R.D.N., owner of MNC Nutrition. Nutrient-dense foods will yield a much bigger payoff for your body.

2. Nighttime calories count more

Those midnight munchies can take a toll. Researchers found subjects who snacked later in the day had a greater tendency to put on weight, and burned less fat than when they stopped eating by 7 p.m.

3. We all absorb calories differently

You and your BFF might both order the same serving of ice cream, but due to differences in genetics, enzyme levels, gut bacteria, and even intestinal length, you might take in more calories.

Fire up more energy!

Want to know how many calories you’re burning in a workout? Pay attention to your breathing: “The same way we need oxygen to burn, your body needs oxygen to burn calories. Generally speaking, the harder you’re breathing during exercise, the more calories you’re burning,” explains Nancy Clark, M.S., R.D., a sports dietitian near Boston. The most efficient activities are those that engage the most muscles. Consider the following top calorie-burners*:

  • Running (8:30-mile pace): 325
  • Jumping rope: 260
  • Biking (vigorous effort): 260
  • Rowing (vigorous effort): 250
  • Circuit Training: 235
  • Boxing: 230

*Based on a 130-lb woman for 30 minutes.

How many calories do you need?

2,000: The number of calories the average woman requires each day

2,400: The approximate number of calories for an active woman

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