Published by the Students of Johns Hopkins since 1896
May 26, 2020

Recent dietary guidelines include significant changes

By Jonathan Grover | September 12, 2002

On Sept. 5, a panel of 21 scientists and physicians at the National Academy of Science's Institute of Medicine released new recommended dietary guidelines. The guidelines stray from previous versions as they not only allow flexibility in the amounts of fats, carbohydrates and proteins consumed, but also account for exercise.

Previous targets included 50 percent or more of total calories coming from carbohydrates, and 30 percent or less coming from fats. The new recommendations follow a range: 45 to 65 percent of calories should come from carbohydrates, while 20 to 35 percent should come from fat.

On the other hand, while the suggested amount of protein consumption remained constant at 10 to 35 percent of total calories, a new standard was introduced. Women should be consuming 25 grams of fiber daily, while men should aim for 38 grams.

Of all the suggestions, however, it is the exercise guidelines which are most striking. The panel believes that people should be engaging in at least an hour of physical activity each day. While this may seem to be a relatively reasonable amount, it should be noted that it is twice as much as the surgeon general recommends.

One might observe that not all forms of exercise are equally strenuous. That being the case, the guidelines recommend moderate activity for an hour. Such activity might include walking at a pace of approximately 4 miles per hour, leisurely swimming or bicycle riding. The exercise can, nonetheless, be broken up throughout the day. For those who can not devote an hour each day, 20 to 30 minutes of high-intensity exercise, four to seven times weekly should accomplish the same results.

The study, conducted at the request of Congress and other U.S. government agencies, as well as Health Canada, comes as both nations have begun to address a national health concern: obesity. Now reaching epidemic levels in the United States, the obesity issue has typically been addressed with low-fat foods that are generally high in calories, but low in fiber. However, for an epidemic that results in approximately 300,000 deaths yearly, it was obvious that something more needed to be done.

As Dr. Benjamin Caballero of Johns Hopkins University readily pointed out, "We must distinguish between diets to lose weight and diets to maintain health ... Our report focuses on diet for the long term to maintain health."

Still, the study directly addresses obesity in the following manner: while fat is noted as a major source of energy in a diet, people are urged to avoid certain types of fats which are linked to an increased risk in heart disease. These include saturated fats and trans fatty acids.

Saturated fats are often found in meat and dairy products, while trans fatty acids are in the hydrogenated oils that are commonly used in cookies, crackers and other processed foods.

By contrast, healthy fats have been emphasized. These included two types of polyunsaturated fats which have been studied to reduce death from heart disease.

The guidelines for these fats, a new addition, suggests that they be consumed daily.

Key to the report is the balance between diet and exercise. For example, a relatively inactive 30-year-old woman standing approximately 5 feet 5 inches tall and weighing between 111 and 150 pounds should be consuming between 1,800 and 2,000 calories daily. The same woman participating in the recommended exercise regimen should aim to consume between 2,500 and 2,800 calories daily.

"To reduce some of the main killers of America, we will have to increase the level of physical activity," said Dr. Caballero.

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