Weekends Not a Friend to Weight Loss, Study Shows

Weekends can slow down healthy eating plans and weight loss, according to a study reported in the journal Obesity.

Researchers found that participants on strict diet and exercise programs tend to lose weight more slowly than expected because they eat more on weekends than during the week.

Past research had confirmed that people tend to gain weight during the holidays, particularly between Thanksgiving and New Year's, but this is the first study to carefully monitor daily body weight, calorie intake, and calorie expenditure for several weeks throughout a year.

The study also demonstrates that increased caloric intake is not just a problem during the holidays. It also happens on most weekends.

"We thought weekends would present a problem for some people attempting to lose weight, but the consistency of our finding before and during the interventions was surprising," says author Susan B. Racette, Ph.D., at Washington University School of Medicine in St. Louis.

"Subjects in the diet group lost weight during the week, but over the weekend, they stopped losing weight because they were eating more," says Dr. Racette.

People Did Not Realize Extra Consumption

Dr. Racette's team followed 48 adults between the ages of 50 and 60 who took part in the CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) study.

Body mass index (BMI) ranked subjects as overweight or healthy weight when the study began. None were classified as obese.

Earlier studies demonstrated that mice and rats live longer, healthier lives when on a calorie restricted diet.

The CALERIE study is designed to determine whether taking in fewer calories over a long time period will slow down or reverse some of the common markers of aging and disease.

"But rats don't have weekends the way people do," says Dr. Racette. "On weekends, human lifestyle patterns can be very different. People have social events, parties to attend, and if they have children who play sports, they might be at fields all day long, relying on concession stands for food."

Study participants were divided into three groups: the first lowered their daily calorie intake by 20 percent, a second increased daily physical activity by 20 percent, and a third control group did not change diet or activity levels.

All three groups were monitored for one year. They kept food diaries, tracked exercise with accelerometers, and were weighed regularly.

Dr. Racette says people in the study did not always realize they were eating significantly more food on weekends.

"It was surprising how consistent the findings were," she says. "We also were surprised by the dramatic way in which weekends continued to slow weight loss throughout the course of the study."

Before the interventions began, the researchers established "baselines" for each study participant's exercise and eating habits. This pre-intervention data determined that participants consumed the most calories on Saturdays.

An average of 36 percent of their total calories came from fat on Saturdays, but less than 35 percent came from fat during the rest of the week. The typical weekend weight gain before the diet and exercise interventions began would have led to an average increase of nine pounds a year.

When study participants were asked either to cut calories by 20 percent or to increase activity by a like amount, the pattern remained the same.

Those in the calorie restriction group took in more energy on Saturday. Those in the exercise group ate more on both Saturday and Sunday.

As a result, people in the calorie restriction group stopped losing weight on weekends, and those in the exercise group actually gained weight on weekends.

"People on diets often don't lose as much weight as we would expect, and this finding helps to explain why," she says.

Careful Planning and Light Snacks Help

As the researchers move into the second phase of the CALERIE study, looking at more subjects over a longer period of time, they now recommend that participants weigh themselves daily in order to be more aware of their patterns of weight loss and weight gain, particularly on weekends.

For those not in a research study, she recommends moderation and careful planning to avoid weekend pitfalls.

"Planning ahead can't be emphasized enough," Dr. Racette says.

She recommends packing healthy food if you are running errands, eating a little something so you are not starving when you arrive at a party, even packing a light lunch before going to the kids' ballgames so that you have a choice other than junk food at a concession stand.

"In addition, she says, "paying closer attention to portion sizes can enable a person to enjoy the weekend without sabotaging weight-control efforts."

Always consult your physician for more information.