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Sweetened drinks raise women's risk for obesity, type 2 diabetes

Overweight, obesity, and type 2 diabetes — all of which increase the risk for heart disease and other complications — have been on the rise in the United States for nearly 30 years. During this same period, our calorie intake from sugary drinks has increased 135%. Coincidence? Probably not. Studies in children have found a strong association between obesity and sweetened soft drinks, but similar data on adults was unavailable for a time. A 2004 study from the Harvard School of Public Health helps fill in the blanks, at least for women.

In the August 25, 2004, Journal of the American Medical Association , Harvard researchers reported that over an eight-year period, women who consumed more soft drinks gained more weight. Specifically, they found that women whose consumption rose from one drink or less per week to one or more daily gained more than twice as much weight (averaging almost 18 pounds) as women who limited their consumption to no more than one drink per week. One sugar-sweetened soft drink or more per day was also associated with an 83% increase in risk for type 2 diabetes, compared to an intake of less than one such drink per month. Similar consumption of fruit-flavored punch (which can contain as little as 5% juice) doubled the risk of type 2 diabetes. Diet sodas and true fruit juices did not pose these risks.

The data came from the Nurses' Health Study II, in which researchers have followed subjects for many years and carefully noted changes in dietary habits. Women who increased their intake of sweetened soft drinks also consumed more total calories, which suggests they did not eat less solid food to compensate.

But the effect of soft drinks on weight gain and type 2 diabetes involves more than extra calories. These beverages have a high glycemic index, which means they are digested quickly, producing a brief spike in blood sugar levels, and may not satisfy hunger for long. The Harvard study suggests that sweetened drinks may even increase hunger. Consuming such drinks can also lead to elevated insulin levels.

The fiber content of a true fruit juice such as orange juice gives it a lower glycemic index than sugar-sweetened beverages. Real fruit juices do have calories, but they also contain vitamins, minerals, and phytochemicals that may play a role in improved metabolism or weight control. Foods with a significant protein, fat, or fiber content also have a lower glycemic index than soft drinks.

Another 2004 study — one on trends in beverage consumption from 1977 to 2001 — suggests a related cause of weight gain. Nutrition experts at the University of North Carolina found that while Americans consume more and more sweetened beverages, they are drinking less milk at all ages ( American Journal of Preventive Medicine , October 2004). Milk has obvious nutritional value (which includes protein, calcium, and vitamin D), and although it's not clear why, drinking milk has been associated with reduced weight in a variety of studies.

In light of rising obesity rates and type 2 diabetes, we would do well to cut down on our intake of sweetened soft drinks and juice drinks — admittedly difficult when we're constantly exposed to super-sized temptations. Experts estimate that most people could avoid gaining weight if they cut out 100 calories a day — an amount found in less than a can of soda.

What to do. Quench your thirst with water. If you want a soft drink, stick to diet soda or flavored but unsweetened seltzers. Get regular exercise — at least 30 minutes per day of physical activity such as brisk walking or moderate bicycling. It not only burns extra calories but also reduces the risk for type 2 diabetes.

December 2004 Update

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