New guidelines on diet and exercise
May 13, 2003 | 12:00am
When the prestigious US Institute of Medicine (IOM) released its new nutrition and exercise guidelines for healthy people last September, it upset many of the standard recommendations for a healthy lifestyle. The IOM’s hefty new two-volume report on what to eat – the first from the institute since 1989 – gives ranges on how much and what kind of food healthy people (not people looking to lose weight) should consume, instead of prescribed amounts. "The beauty of this report is that it gives people tremendous flexibility in their diets," comments Penny Kris-Etherton, Ph.D., R.D., a member of the panel who wrote the report and a professor of nutrition at Pennsylvania State University.
But that flexibility comes at a price. For the first time, the IOM also links the amount of food people consume to their level of activity, recommending that everyone gets at least one hour a day of moderately intense physical activity – twice the 30 minutes per day suggested by the US Surgeon General in 1996. And that may seem like a lot to many people who’ve religiously managed to work in their half-hour "on most, if not all, days of the week," as suggested by the Surgeon General. So the question is, how do we apply the new guidelines?
Compared to earlier recommendations, the new guidelines offer greater latitude in the mix of fats, carbohydrates, and proteins – collectively known as macronutrients – that make up a person’s diet. The report suggests that adults can meet their energy and nutrient needs and reduce their risk of developing chronic diseases by eating 20 percent to 35 percent of calories from fats, 45 percent to 65 percent from carbohydrates, and 10 percent to 35 percent from protein.
Earlier advice had capped fat intake at 30 percent of total calories and set a lower limit of 50 percent for carbohydrates. But studies have since shown that low-fat, high carbohydrate diets can reduce high-density lipoprotein ("good") cholesterol, increase triglycerides (an independent risk factor for heart disease), and may increase the glycemic load of a meal, a risk factor for chronic conditions such as diabetes and heart disease.
High-fat diets, on the other hand, may lead to weight gain and harmful intake of saturated fats (from meats and full-fat dairy products, for example) and trans fatty acids (trans fats), found in hydrogenated vegetable oils used in many commercially baked goods and snacks. Both saturated and trans fats raise levels of low-density lipoprotein ("bad") cholesterol and can increase the risk for cardiovascular disease. The nutrition panel says there is no safe level of trans fatty acid intake, and it recommends eating as little saturated fat as possible.
The IOM report advises replacing these fats with "good" ones. Monosaturated and polyunsaturated fatty acids can help lower cholesterol and cardiovascular risk. The new guidelines establish, for the first time, recommended levels of two types of polyunsaturated fatty acids: alpha-linolenic acid (an omega-3 fatty acid) and linolenic acid (an omega-6 fatty acid). The body needs both, but can’t make them, so they must come from food. The panel advises an adult person to get 12 grams/day of omega-6 fatty acids (found in soybean, safflower, and corn oils, and in nuts and seeds) and 1.1 grams/day of omega-3 fatty acids (found in soybean, flaxseed, and canola oils and cold-water fishes such as salmon, tuna, and sword fish).
The IOM also makes its first fiber recommendation, advising those under age 50 to consume 25 grams/day, and those over age 50 to get 21 grams/day. Most healthful fiber comes from nondigestible carbohydrates in plants. Food sources include sweet potatoes, legumes, whole grains, cereal products, onions, and some fruits. While it has no nutrients, fiber is healthy because it hastens the movement of waste through the intestines, inhibits fat and cholesterol absorption, and slows digestion, which can curb hunger and possibly blood sugar response.
The report advises that we get no more than 25 percent of calories from added sugars, such as those found in soft drinks and candy. Above this level, sugar consumption may interfere with our getting enough vitamins and minerals. The new guidelines reaffirm the previous recommended protein intake of 0.8 grams/day per kilogram (about 0.4 grams/day per pound) of body weight.
As IOM committee member and Harvard School of Public Health scientist Eric B. Rim, Sc. D., explains, "We can’t give recommendations on how much to eat unless we also comment on how much to burn." Based on studies on physical activity and exercise, the panel concluded that healthy people should get at least 60 minutes a day of moderately intense exercise, such as walking at a four-mile-per-hour pace. Equivalent activities include calisthenics without weights, golf without a cart, slow swimming, and leisurely bicycling. Housework and yard work can also be moderately intense but the IOM is clear that the 60 minutes of exercise needs to be in addition to such activities.
An hour a day is twice the amount suggested by the Surgeon General in 1996 (and endorsed by many health groups). IOM panel members acknowledge that 30 minutes a day helps, but they say it’s not enough to maintain a healthy weight and to achieve the maximum health benefits of exercise.
Exercise produces many benefits, and different amounts may fulfill different purposes. People who have managed to fit in 30 minutes of exercise on most days of the week are already reducing their risk of heart disease, diabetes, osteoporosis, and elevated blood pressure. Just recently, Dr. JoAnn Manson of the Harvard Medical School authored a study published last year in the New England Journal of Medicine, which compared walking to vigorous exercise in nearly 74,000 women, ages 50-74. She and her colleagues found that women who either walked briskly or exercise vigorously for at least 2.5 hours per week reduced their risk of developing cardiovascular disease (CVD) by 30 percent. Another study, authored by exercise expert Dr. I-Min Lee and published in 2001 in the Journal of the American Medical Association, found similar results in 40,000 women.
Still, exercising at moderate intensity for a longer period of time – one hour every day – not only reduces our risk for chronic conditions such as CVD but also maximizes and adds to those benefits (lowering risk for colon cancer, for example). And it helps keep weight in a healthy range.
Health experts would like to see everyone get moving, especially in the light of the rapid rise in the incidence of overweight and obesity. The IOM’s new exercise advice may advance that cause, especially among people who are already somewhat active. But both Drs. Manson and Lee worry that it may set the bar too high for busy people, perhaps discouraging them from exercising at all and enjoying the proven benefits of 30 minutes of moderate-intensity activity on most days of the week.
Nearly two-thirds of Filipinos are not physically active on a regular basis and as much as 20 percent are completely sedentary. So in general, we are not able to fulfill the required optimum intensity and frequency for healthy exercises. Sixty minutes of exercise per day is no doubt better than 30 minutes, but any exercise at all is better than none. Sedentary people can find reassurance (and perhaps inspiration) in extensive research that has shown substantial benefits from 30 minutes a day of walking – a common form of exercise. Walking is accessible to nearly everyone, doesn’t require classes or fancy equipment, and could very well lead to an even greater exercise commitment.
The message from food and exercise scientists is clear: It’s not just what and how much we eat that is important. We need to balance that with the calories we burn through proper exercises.
But that flexibility comes at a price. For the first time, the IOM also links the amount of food people consume to their level of activity, recommending that everyone gets at least one hour a day of moderately intense physical activity – twice the 30 minutes per day suggested by the US Surgeon General in 1996. And that may seem like a lot to many people who’ve religiously managed to work in their half-hour "on most, if not all, days of the week," as suggested by the Surgeon General. So the question is, how do we apply the new guidelines?
Earlier advice had capped fat intake at 30 percent of total calories and set a lower limit of 50 percent for carbohydrates. But studies have since shown that low-fat, high carbohydrate diets can reduce high-density lipoprotein ("good") cholesterol, increase triglycerides (an independent risk factor for heart disease), and may increase the glycemic load of a meal, a risk factor for chronic conditions such as diabetes and heart disease.
High-fat diets, on the other hand, may lead to weight gain and harmful intake of saturated fats (from meats and full-fat dairy products, for example) and trans fatty acids (trans fats), found in hydrogenated vegetable oils used in many commercially baked goods and snacks. Both saturated and trans fats raise levels of low-density lipoprotein ("bad") cholesterol and can increase the risk for cardiovascular disease. The nutrition panel says there is no safe level of trans fatty acid intake, and it recommends eating as little saturated fat as possible.
The IOM report advises replacing these fats with "good" ones. Monosaturated and polyunsaturated fatty acids can help lower cholesterol and cardiovascular risk. The new guidelines establish, for the first time, recommended levels of two types of polyunsaturated fatty acids: alpha-linolenic acid (an omega-3 fatty acid) and linolenic acid (an omega-6 fatty acid). The body needs both, but can’t make them, so they must come from food. The panel advises an adult person to get 12 grams/day of omega-6 fatty acids (found in soybean, safflower, and corn oils, and in nuts and seeds) and 1.1 grams/day of omega-3 fatty acids (found in soybean, flaxseed, and canola oils and cold-water fishes such as salmon, tuna, and sword fish).
The report advises that we get no more than 25 percent of calories from added sugars, such as those found in soft drinks and candy. Above this level, sugar consumption may interfere with our getting enough vitamins and minerals. The new guidelines reaffirm the previous recommended protein intake of 0.8 grams/day per kilogram (about 0.4 grams/day per pound) of body weight.
An hour a day is twice the amount suggested by the Surgeon General in 1996 (and endorsed by many health groups). IOM panel members acknowledge that 30 minutes a day helps, but they say it’s not enough to maintain a healthy weight and to achieve the maximum health benefits of exercise.
Exercise produces many benefits, and different amounts may fulfill different purposes. People who have managed to fit in 30 minutes of exercise on most days of the week are already reducing their risk of heart disease, diabetes, osteoporosis, and elevated blood pressure. Just recently, Dr. JoAnn Manson of the Harvard Medical School authored a study published last year in the New England Journal of Medicine, which compared walking to vigorous exercise in nearly 74,000 women, ages 50-74. She and her colleagues found that women who either walked briskly or exercise vigorously for at least 2.5 hours per week reduced their risk of developing cardiovascular disease (CVD) by 30 percent. Another study, authored by exercise expert Dr. I-Min Lee and published in 2001 in the Journal of the American Medical Association, found similar results in 40,000 women.
Still, exercising at moderate intensity for a longer period of time – one hour every day – not only reduces our risk for chronic conditions such as CVD but also maximizes and adds to those benefits (lowering risk for colon cancer, for example). And it helps keep weight in a healthy range.
Health experts would like to see everyone get moving, especially in the light of the rapid rise in the incidence of overweight and obesity. The IOM’s new exercise advice may advance that cause, especially among people who are already somewhat active. But both Drs. Manson and Lee worry that it may set the bar too high for busy people, perhaps discouraging them from exercising at all and enjoying the proven benefits of 30 minutes of moderate-intensity activity on most days of the week.
Nearly two-thirds of Filipinos are not physically active on a regular basis and as much as 20 percent are completely sedentary. So in general, we are not able to fulfill the required optimum intensity and frequency for healthy exercises. Sixty minutes of exercise per day is no doubt better than 30 minutes, but any exercise at all is better than none. Sedentary people can find reassurance (and perhaps inspiration) in extensive research that has shown substantial benefits from 30 minutes a day of walking – a common form of exercise. Walking is accessible to nearly everyone, doesn’t require classes or fancy equipment, and could very well lead to an even greater exercise commitment.
The message from food and exercise scientists is clear: It’s not just what and how much we eat that is important. We need to balance that with the calories we burn through proper exercises.
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