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Weight Loss and Control (cont.)

Nutrition 101

Weight gain is caused by consuming more calories than the body uses.

  • The average person uses as many as 2,500 calories daily, or 17,500 calories per week.
  • If you eat the amount your body needs, you will maintain your weight. It takes 3,500 extra calories to gain 1 pound.
  • To lose weight, you must consume fewer calories than your body uses. You must eat 3,500 calories less than you need, say 500 calories per day for one week, to lose 1 pound.

Calories count. It's important to understand where calories come from and how to make the smartest food selections. Here are some basics:

  • Foods are composed of the following three substances, in varying amounts:
    • Carbohydrates (four Calories per gram): Examples include grains, cereal, pasta, sugar, fruits, and vegetables.
    • Protein (four Calories per gram): Examples include legumes (beans, dried peas, lentils), seafood, low-fat dairy, lean meats, and soy products such as tofu.
    • Fats (nine Calories per gram): Examples include whole-fat dairy products, butter, oils, and nuts.

Alcohol is a separate fourth group (seven calories per gram).

A calorie is the amount of energy (heat) needed to raise the temperature of 1 gram of water by 1 degree Celsius. A kilocalorie (or Calorie with a capital C) is the amount of energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius.

  • The energy contained in food is measured in kilocalories but is commonly referred to on food packages and elsewhere as calories.
  • Most people underestimate the number of calories they consume by about 30%.
  • Calculate the number of calories you should consume each day to keep your weight the same.
    • If you are moderately active, multiply your weight in pounds by 15.
    • If you are sedentary, multiply by 13 instead.
    • To lose weight, you need to eat less than this number.

Excess calories from any source (even fat-free foods) will turn into body fat.

  • Any carbohydrate not immediately used for energy will be stored in the liver as glycogen for short-term use. The body has only a limited number of liver cells to store the glycogen. Whatever is left over will be converted to fat.
  • Excess protein and fat in the diet are also stored as fat.

Fat cells are no longer thought to be responsible only for energy storage and release.

  • They synthesize the hormone leptin, which travels to the hypothalamus in the brain and regulates appetite, body weight, and the storage of fat.
  • Leptin was first discovered in 1994. The exact way it works is not yet fully understood.
  • Disorders of leptin account for only a few cases of obesity, usually morbid (extreme) obesity.
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