Weight Loss and the USDA's Exercise Recommendations Explained

The U.S. Department of Agriculture’s Food Guide Pyramid recommends that adults get a minimum of 30 minutes of moderate activity a day, which includes walking at 3.5 mph, gardening, golfing or even a light gym workout. While the 30 minute a day recommendation is a good for promoting health, it is not so good for promoting weight loss and here’s why.

According to the Mayo Clinic’s Exercise for Weight Loss: Calories Burned in One Hour, a 160-pound person who takes a 30-minute walk and maintains a pace of 3.5 miles per hour will only burn about 138.5 calories per walk. In order to lose one pound of body fat, it is necessary to burn 3,500 calories above what the body needs for fuel.

How Much Walking is Necessary to Lose One Pound?

A 160-pound person who never consumes any calories above his/her Basal Metabolic Rate (the estimated minimum number of calories his/her body needs to function) will have to walk for about 25.3 days in order to burn the 3,500 calories necessary to lose one pound. That does not bode well for motivation especially since the accepted norm for safe and healthy weight loss is .5-2 pounds per week. Worse, this scenario isn’t even realistic for three reasons.

First, it doesn’t take into account that people tend to vary their walking pace due to traffic, other people, temperature, environmental conditions and energy level. Second, nobody is perfect and even with the best of intentions, there will always be days when caloric intake exceeds caloric need (birthdays, graduations, office parties, anniversaries, emotional eating, etc.). Third, Basal Metabolic Calculators aren’t very accurate.

The Truth About Basal Metabolic Rate Calculators and Caloric Need

Basal Metabolic Rate Calculators are designed to provide a best guess estimate of a person’s daily caloric need based on age, height, weight and perceived daily activity level. Since no two people are the same and no two bodies will burn calories at the same rate, there is room for error and sometimes even a considerable amount of error.

For example, take two woman who are both 5’6″ tall, 145 pounds and moderately active. According to a BMR calculator, each has a daily caloric need of 1,500 calories. Both women change their diets and maintain a 1,500 calorie diet. One woman loses weight, the other does not. It’s part of the margin of error.

Even calculators that calculate the number of calories burned while doing certain activities are only best guess estimates based on age and weight. A treadmill’s computer may estimate that a 160 pound person will burn 138 calories in 30 minutes of walking, but that number can be considerably off, too, in either direction. Again, every body is different and will every body will burn calories at a different rate.

No Cushion for the Margin of Error

Being off even a few calories per day can make the difference between successful weight loss, no weight loss and even weight gain. This is a key factor that the U.S.D.A.’s 30 minutes a day moderate exercise recommendation doesn’t consider. One hundred and thirty eight calories burned per day doesn’t provide much window for the margin of error found in both BMR and calorie calculators. It also doesn’t provide enough of a cushion to ensure weight loss despite an occasional dietary indulgence.

One hundred and thirty eight calories is equivalent to:

  • .5-.75 serving of most cereals
  • .75 serving of peanut butter
  • .5 serving of an energy bar
  • 1.3 sodas
  • .25 serving of chocolate cake
  • 1.3 servings of pretzels
  • .9 servings of vanilla ice cream
  • .8 servings of Ranch dressing
  • 1.3 light beers
  • 1 serving of orange juice

Recommendations for How to Lose Weight

The best way to cope with the relative inaccuracy of BMR and calorie calculators is to factor in a larger margin of error than the U.S.D.A.’s Recommendations do by simply adding more daily activity.

  • Replace 30 minutes of moderate activity to 30-90 minutes of vigorous, challenging, metabolism boosting exercise per day. The more challenging an activity, the more calories the body will burn.
  • If unable to perform vigorous exercise due to health reasons, then increase the duration of moderate exercise from 30 minutes to 60-90 minutes per day.
  • Strength train three days per week. At rest, fat burns about two calories per pound per day while muscle burns about six calories per pound per day.
  • Diets don’t work, so instead eat a well-balanced diet, monitor food intake and limit consumption of pre-packaged convenience foods, restaurant meals and fast food.
  • And finally, if diet and exercise don’t seem to work, be sure to consult a doctor because certain medical conditions and medications can have a profound effect on a person’s ability to lose weight.

In conclusion, the U.S.D.A.’s recommendation of 30 minutes per day of moderate exercise is not enough to promote weight loss, especially when considering the margin of error in basal metabolic rate calculators and calories burned calculators. The solution is to get at least an hour or more of exercise every day.

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