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Eat Less -- Live Longer

The Clock of Life

Wisdom of the Worms

How to Make a Nose

Use It or Lose It

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Never Say Die:
Eat Less -- Live Longer

Since the 1930s, scientists have known that lab animals on high-nutrition, restricted-calorie diets live longer lives. But until the era of biotechnology, they couldn't explain why. New genetic research in mice and monkeys may provide some answers. Is it possible that eating too much damages the cells and causes them to become old before their time?

Curriculum Links
National Science Education Standards
Discussion: Food and Calories
Activity 1: Calorimetry Lab
Activity 2: Evaluate Your Favorite Food
Eat Less, Live Longer?



cell structure




(Please visit the Subject-Area Search feature on this website for related Frontiers shows and activities!)


5-8: Structure and Function in Living Systems; Reproduction and Heredity
9-12: The Cell; The Molecular Basis of Heredity; Matter; Energy and Organization in Living Systems
5-8, 9-12: Understandings About Science and Technology
5-8: Personal Health; Science and Technology in Society
9-12: Personal and Community Health; Science and Technology in Local, National and Global Challenges
5-8: Science as a Human Endeavor; Nature of Science; History of Science
9-12: Science as a Human Endeavor; Nature of Scientific Knowledge; Historical Perspectives


All living things require energy to survive. In animals, this energy is derived from the food they eat. All animals, human and non-human, use this food energy to grow, develop and reproduce. Through its metabolism, an organism maintains a balance between energy consumption and production. The standard measure of heat energy is the calorie. Physicists refer to one calorie as the amount of heat necessary to heat one gram of water one degree Celsius.

When nutritionists (and the rest of us) use the term, they mean 1,000 times as many calories, or one kilocalorie -- referred to as either a kcal or Calorie (capitalized). For example, a banana-nut muffin might contain 200,000 calories, but for ease of calculation, we divide that figure by 1,000 and refer to its 200 Calories or kcal.

People need three types of foods or macronutrients: carbohydrates, proteins and fats. (Micronutrients in the form of minerals and vitamins are also essential.) Macronutrients are broken down in the digestive system and transported into the bloodstream, where they are delivered to cells and used for energy.

Each of the different macronutrients produces different amounts of energy. Proteins and carbohydrates yield 4 Calories (kcal) per gram. Fats yield 9 Calories per gram.

Each macronutrient plays a role in promoting health. Proteins and fats are essential to provide amino-acid building blocks for body proteins and to build, maintain and repair tissues. Carbohydrates are a necessary energy source found in vegetable and grain products. Nutritionists, dieticians and doctors agree that people must consume a variety of foods to fulfill their daily caloric requirements.

Although it may seem paradoxical, scientists have known since the 1930s that animals on calorie-restricted (CR) diets often live up to 50% longer than normal. As you'll see on Frontiers, several studies confirm that diets low in calories and high in nutrients extend the life span -- and bring about a number of health benefits. The work of the scientists seen in this episode suggests that overeating may accelerate aging. Physician and longevity researcher Roy Walford has followed a calorie-restricted but nutrient rich diet for many years. Geriatric investigator Richard Weindruch is studying effects of CR in rhesus monkeys and rodents. The research animals receive essential nutrients, but their calories are limited.


A calorimeter is a device that measures the transfer of heat energy during a chemical or physical change. One type of calorimeter contains a combustion chamber surrounded by water. When matter is placed in the chamber and physically or chemically changed (typically, by burning), the temperature change of the water is measured and used to determine the energy (calorie) content of the sample.

In this activity, you'll make and use a simple calorimeter to measure calories.


  • coffee or other large metal can
  • soup or other small metal can
  • marshmallows
  • piece of cork
  • needle
  • hammer
  • nail
  • wire coat hanger
  • 50 ml water at room temperature
  • thermometer
  • matches/lighter
  • gloves or forceps

This lab should only be performed under supervision by a teacher or lab instructor.

Handle hot items with gloves or forceps.

Be sure the room is well ventilated.


  1. Remove both the top and bottom ends of the large can and the top of the small can. Using the hammer and nail, punch two holes at the top of both the large and small cans on opposite sides. Punch a few more holes along the bottom of the large can.

  2. Straighten the coat hanger and thread it through the holes in the top of the two cans so the smaller can hangs inside of the larger can.

  3. Put the marshmallow on one end of the needle and push the other end securely into the piece of cork. Place it inside the big can directly under the suspended small can.

  4. Pour the water into the small can. Measure and record the temperature of the water in degrees Celsius.

  5. Light the marshmallow on fire. Let it burn it out.

  6. Measure and record the temperature of the water in degrees Celsius.

To calculate the number of calories in the marshmallow, multiply the mass of the water in grams by the temperature change in degrees Celcius.

Mass of H2O (grams) x (heated temperature - original temperature) = # of calories 1000 = # of food Calories in the marshmallow.


  1. How does your answer compare with the calorie content provided on the nutrition facts label on the marshmallow packaging?

  2. There is still energy left in the unburned portion of the marshmallow. Some heat will be lost during the experiment. Devise a way to make the calorimeter more efficient.

  3. Conduct the experiment using other foods that are high in fat (e.g., walnuts). What do you think would happen if you tried this experiment with low-calorie or low-fat foods? Conduct an experiment to find out.


Obtain the "Nutrition Facts" label from your favorite type of prepackaged food and study it. Find the following information and place it into a data table:

  • serving size (grams)
  • servings per container
  • total fat (grams)
  • total protein (grams)
  • total carbohydrates (grams)
Calculate the total calories and the overall percentage of each of the macronutrients. Proteins and carbohydrates have 4 Calories per gram and fats have 9 Calories per gram. Multiply the amount of each macronutrient (in grams) by the Calories/gram. Then divide by the Calories per serving to find the percentage of total calories represented by each of the macronutrients. (NOTE: The total number of calories may not match that on the label because of rounding.)


  1. Find out the Recommended Daily Allowance of Nutrients for your age.

  2. Evaluate the nutrition content of various "fast foods" and compare the calories and nutrient values of different foods; for example, salads, burgers, fries, so-called "low-fat" foods.

  3. Find out more about Walford's diet and research on his website, You'll find a database containing nutritional information, recipes, meal plans and links to other sites about aging research and Biosphere 2.

  4. Food diaries can be very revealing. Just for fun, keep a careful record of what you eat and drink for a few days or a week. Record the total amount of calories and nutrients. (You may wish to use the nutrition database on Walford's website.) Then determine how your diet would look with 40% fewer calories. How difficult would it be to get the Recommended Daily Allowance of nutrients on this low-cal diet?

  5. To learn more about Weindruch's work, visit the Institute of Aging at UW-Madison at

  6. Investigate the role of oxygen in the production of free radicals. To observe an example of the effects of oxidation, slice an apple in half and expose it to the air.

Both Roy Walford and Richard Weindruch have been studying the biology of aging and, in particular, the effects of calorie-restricted diets on the aging process, for decades. Walford's "Anti-Aging" diet is based on many years of experimentation. Walford doesn't just eat less -- he eats specific foods that provide high quantities of essential nutrients with minimal calories. Food combinations and menus are calculated by a computer, so that the Recommended Daily Allowances of all essential nutrients are provided. Results of these studies are not considered conclusive and should not suggest that people follow a severe diet regimen, especially one that does not provide essential nutrition. Eating a calorie-restricted diet that deprives adolescents of vital nutrients is not recommended.

Frontiers does not endorse any particular diet or eating program. Remember, the stories you see on this episode are long-term research projects and experiments being conducted to learn more about aging.


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