In one of them, scientists from Penn State University found that people eat more food when served larger portions over time, instead of naturally cutting back to compensate. When presented with larger-than-normal portions over an 11-day period, people consumed an average of 16 percent more calories per day during the period. The only food group that the study participants did not eat more of was fruits and vegetables. Their conclusion: It doesn’t matter if you’re obese or lean or if you were brought up to be a plate-cleaner or not," says Barbara Rolls, PhD, professor of nutritional sciences at the Pennsylvania State University. "The bigger the portion, the more people eat . . . and they’re not even aware of it."
In another study, Brown Medical School scientists found that snacking on foods packaged as individual servings doesn’t lead people to eat less than they would if eating the same food out of a large bag or box. In this study, it seems that it’s the total amount of food available, not the package or portion size which provides the main cue for how much to eat. This is a problem during Christmas when more food is available on our table than almost anytime during the year.
There’s a simple equation here: Foods high in energy density, such as candy bars and soda, tend to put on weight, while high-water foods tend to take it off. "There is an inverse relationship between energy density and the water content of foods," says Adam Drewnowski, PhD, director of the Center for Public Health Nutrition at the University of Washington in Seattle.
A new study of Dr. Rolls found that cutting calorie density and portion size was more effective than either strategy alone. The study, conducted among two dozen women aged 19-35, found that participants ate 812 fewer calories a day by trading calorie-dense dishes for high-volume foods and eating smaller portions – without feeling deprived or hungry at the end of the day. Cutting down on calorie density foods (like many of our Christmas dishes) was more effective than portion control, according to the study published in the January 2006 issue of the American Journal of Clinical Nutrition.
Following a strict low-carbohydrate diet for six months will take weight off, but by 12 months, it creeps back on, says Alice H. Lichtenstein, DSc, professor of nutrition at Tufts University. A low-carbohydrate diet "is difficult to achieve for long periods of time," says Dr. Lichtenstein. Many low-carb diets are high-protein, modeled on the Atkins approach, which relies on meat, eggs, and dairy products while mostly eliminating a large category of foods and the nutrients they contain without taking into account "good" carbs like whole grains.
The secret appears to be variety in food. "The more varied the food, the more you eat," says Dr. Rolls. "So, use variety to work for you." People who have the most body fat eat a greater variety of most foods than others.
In other words, stock six kinds of cookies in your cupboard and the variety might tempt you to eat more than if you had only one. "If people are offered three different kinds of sandwiches, they’ll eat more than if they are given three of the same sandwiches," says Susan Roberts of the Human Nutrition Research Center of Tufts University.
The exception: "People who eat the greatest variety of vegetables have the least body fat," adds Roberts. So, this Christmas, focus on a few foods spread out on the table and limit your intake only to those foods.
A study from Columbia University found that people who slept four or fewer hours per night were 73 percent more likely to be obese than those who slept between seven and nine hours each night. Those who slept for five hours at night had a 50 percent higher risk of being obese than those getting a full night’s sleep. Other studies show that leptin levels dip when people are sleep-deprived, leading to increased appetite. So, this holiday season, try to get sufficient sleep in spite of your busy schedule.
The study followed 191 adult women who were assigned to one of four exercise regimens, along with a low-calorie, low-fat diet. At the end of two years, the women in the highest-duration exercise group lost the most – about 7.2 percent of their initial body weight. Dieters need to sustain about 270 to 300 minutes of exercise a week to achieve and maintain weight loss, said John Jakicic, lead author of the study.
It’s tough to lose weight and keep it off. But Brown University’s Rena Wing and colleagues have a registry of more than 3,500 people who’ve managed to drop at least 30 pounds and not regain the weight for at least a year.
How do they do it? "They eat a low-fat diet and exercise a tremendous amount," says Wing.
They burn an average of 2,800 calories a week. That’s equivalent to walking four miles a day, though they typically report a mixture of activities, rather than just walking.
So, find time during the holiday season to exercise. Get off your duff and move!