It’s no secret that the United States has a weight problem, but the numbers are staggering: More than a third of U.S. adults are obese. Cases of heart disease, Type 2 diabetes and stroke — which kill hundreds of thousands each year and are linked to obesity — are set to multiply tenfold between 2010 and 2020. By 2030, the annual medical bill for the nation’s bad eating habits could top $66 billion.

Statistics will not scare people into better health, though. “The big question is: How do you encourage folks to eat better?” says Steven Carlson at the U.S. Department of Agriculture.

Carlson and colleagues at the USDA and the Massachusetts Department of Transitional Assistance are trying to answer that question. Through a program called the Healthy Incentives Pilot (HIP), they have put themselves at the forefront of a war on obesity that involves government agencies, researchers and even private industry. The initial results are encouraging.

The idea behind HIP is simple: Make healthful foods more affordable. Over 14 months, from November 2011 to December of last year, 7,500 residents of Hampden, Mass., who get government assistance when buying groceries received 30 cents of food-buying credit for every dollar of their allowance that they spent on fruit and vegetables.

Carlson and his colleagues are still evaluating the scheme, but he says: “We have some pretty strong indications that this investment did increase the amount of fruit and vegetables consumed by these low-income families.”

Elsewhere, the health insurer Humana is offering broad incentives through its Vitality initiative. Clients who sign on have their health assessed and then collect points for healthful activities. Each time a member visits the gym, for example, he can swipe a card to receive points. “You can use those reward points for an Amazon gift card or a pedometer, or to book a vacation,” says Stuart Slutsky of Humana Vitality.

Humana has started offering Vitality as a standalone product, without insurance, to other companies. Toyota, which employs about 30,000 people in the United States, has enrolled its employees in the program. Some companies have taken things a step further, imposing financial penalties on employees who fail to make the most of the program.

Plans like Vitality have been in place in South Africa and England since the late 1990s, and participants have reaped rewards.

Within a year, for example, firms in South Africa saw employees shedding excess weight; rates of high blood cholesterol also fell.

Trying fat taxes

Another obvious approach is to make unhealthful foods more expensive. But fat taxes don’t go down well. A recent effort to impose a tax of about $2.80 per kilogram of saturated fat in food products in Denmark failed, as Danes started heading over national borders to buy cheap, fatty foods.

Sugar-sweetened beverages, on the other hand, represent a clear-cut target, says Roberta Friedman at Yale University’s Rudd Center for Food Policy and Obesity.

“We’ve got such solid science that shows there is a relationship between consumption of sugar-sweetened beverages and Type 2 diabetes, cardiovascular disease, gout and tooth decay,” she says. “They don’t offer any nutrition . . . and there’s proof they’re damaging to your health.”

Researchers think that a penny-per-ounce tax on sugar-sweetened drinks would significantly reduce their consumption and improve public health. Such a tax would increase the cost of a 20-ounce soda by about 20 percent.

“A 20 percent rise will have a bit of an impact, but it may not be enough,” worries neuroendocrinologist Robert Lustig at the University of California at San Francisco, who treats children with obesity-related illnesses.

But a study published last year offers hope. It concluded that a nationwide penny-per-ounce tax would decrease overall consumption of sugar-sweetened beverages by 15 percent among people age 25 to 64. Over 10 years, such a reduction would avert 95,000 coronary heart events and 8,000 strokes, and it would save more than $17 billion in medical costs alone, the study’s authors claim.

Attempts to put such a tax in place in various states have so far proved unsuccessful.

Eyeing chocolate milk

Tweaking food prices may be the best way to alter eating habits, but playing tricks on the eye works, too.

All it takes for schoolchildren to choose a carton of milk over a chocolate drink, for example, is moving the chocolate drink to the shelf’s back row. “The consumption of chocolate milk goes down because people like to pick up what they see first,” says Kelly Brownell of the Rudd Center.

Similar tactics could be employed to discourage people from overeating.

After age 3, we tend to stop regulating our food intake by when we feel full, and instead finish what’s in front of us. But people do tend to regulate their intake when a serving is partitioned. Individuals ate fewer Pringles, for example, when they encountered a red one after every seven they consumed.

Elongating a package can also lead a person to think he is eating more than he actually is. The same goes for the shape of a vessel a person drinks out of: Taller, thinner glasses can trick a person into thinking he has consumed more than if he had been drinking from a shorter, wider vessel.

— New Scientist