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Americans will sometimes accept a smaller portion in a restaurant to save calories, a new study suggests. And they might even be willing to pay the same price. The study was done by two business professors, not doctors. The setting was a Chinese food restaurant in a hospital. As they went through the serving line, people were asked if they wanted a half-size portion of the rice or noodles that went with the main course. The server told them this would save 200 calories. Some people were offered 25 cents off for choosing the smaller portion. Others got no discount at all. Depending on the day, 14% to 33% of the customers chose the half-size portion. The discount made no difference in how many people accepted. Researchers also weighed the leftovers. They found that people who took half-size portions left just as much food on their plates as those who took full portions.

Parents worry that the distractions of modern life are keeping their kids from getting enough sleep. And it looks like they’ve had the same worry for more than 100 years. A new study took a historic look at recommendations on sleep for kids. The oldest advice was from 1897 and the newest from 2009. The recommended amount of nightly sleep for kids has declined by about 80 minutes in that time. So has the amount of sleep kids actually get. Kids’ average sleep time has been about 37 minutes a night less than whatever was recommended at the time. The authors said sleep needs may vary from child to child. They said parents who wonder if their kids are sleeping enough should watch for signs of daytime sleepiness. The journal Pediatrics published the study online. HealthDay News wrote about it February 13.

A mild zap of electricity to part of the brain may help people to learn better, a new study suggests. Other researchers are hoping this approach someday may help people with Alzheimer’s disease. The study was done on seven people with epilepsy. They originally had electrodes implanted in their brains to help surgeons find the source of their seizures. The new study used these electrodes to stimulate parts of the brain involved in learning. People played a video game that had them take the role of taxi drivers in a small town. They searched for passengers and dropped them off at stores. They were given zaps of electricity when they learned how to find some stores, but not others. They could not feel the stimulation. People found stores faster and by more direct routes if they had learned where the stores were during brain stimulation.

Practicing tai chi may help people with Parkinson’s disease improve their movement and balance and reduce their risk of falls. In a new study, tai chi provided more benefits than two other exercise programs. Tai chi is an ancient Chinese art that involves slow, controlled movements. The study included 195 people with mild to moderate Parkinson’s disease. This disease causes tremors and problems with movement and balance. People in the study were randomly divided into 3 groups. They were assigned to do tai chi, resistance exercise or stretching. Sessions were an hour each, twice a week. The program lasted 24 weeks. The tai chi group showed more improvements than the other groups in balance, control of movement, and the length and speed of people’s stride when walking.

Sitting in coach class doesn’t increase your risk of a blood clot after a long flight, an expert group says. Some people have called these clots “economy class syndrome.” But people in first class have about the same risk, new guidelines say. The guidelines come from the American College of Chest Physicians. They include advice on preventing deep vein thrombosis. This type of clot occurs in the leg. It is more common after a long flight or another long period without movement. The guidelines also cover prevention of clots in the lungs and in arteries. The risk of deep vein thrombosis is very low, the guidelines say. The average risk is 1 out of 1,000 people each year. That risk doubles on flights of at least 8 hours. But you can help prevent these clots if you get up and move around on the flight. Some people have a greater risk.