That's the number of Americans who go on a diet each year — many of them right after the hyperconsumption of the holidays. In fact, vowing to lose weight is one of the most common New Year's resolutions. It's unclear how successful those efforts are, though some experts say as few as 5 percent of dieters manage to keep the weight off long-term. Still, few would deny the impulse is a good one: About 70 percent of adults in the United States are overweight or obese. Excessive weight can lead to a number of health problems, including high blood pressure, heart disease, diabetes, arthritis and sleep disorders. For some people, weight-loss medication or surgery is recommended. For most, though, lifestyle changes — specifically, healthier eating and more physical activity — are considered the best option.