Does this sound familiar? You stick to your diet all week, never letting temptation get the best of you.  But once the weekend arrives, you allow yourself a little “treat” now and then. No harm, right? Wrong!

Recent studies illustrate that eating more than usual on weekends can be just as damaging to your waistline as those of holiday celebrations. Holidays often find us eating more and exercising less, and weekend behavior may be similar. These weekend lifestyle changes may result in weight gain, slower weight loss, and problems maintaining significant weight loss.

A team of researchers recently published the findings of a year-long, government-funded study known as CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) in the journal Obesity. The purpose of CALERIE was to determine whether weekend dietary changes or activity patterns slowed down the aging process and reduced the risk of certain diseases.

The CALERIE study involved 48 older adults between the ages of 50-60. At the start of the study, the researchers measured the participants’ exercise and eating habits, as well as their body mass index (BMI). The participants, none of which were considered obese, took in the most calories on Saturdays. The research team monitored the participants throughout the study, utilizing food diaries, regular weigh-ins, and exercise accelerometers.

Calculating CALERIE’s Findings

The study’s findings found that those older adults on strict diet and exercise programs generally consumed more calories on the weekends than during the week. “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,” said Susan B. Racette, PhD, assistant professor of physical therapy and medicine at the 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.”

For the CALERIE study, the participants were divided into three groups:

• Group 1 took in 20% fewer calories each day, but their activity levels did not change.
• Group 2 increased their daily exercise regimen but didn’t change their diet. This provided them with a comparable energy deficit to Group 1.
• Group 3 did not change their diet or activity level.

The researchers believe that these findings may help explain the relatively slow rates of weight loss that’s often observed in clinical studies. “It was surprising how consistent the findings were,” said Racette. “We also were surprised by the dramatic way in which weekends continued to slow weight loss throughout the course of the study.”

CALERIE’s findings may illustrate why it’s so difficult to keep lost weight off permanently. Experts advise that careful planning is necessary to ensure that dieters not consume too many calories during weekends. They also recommend controlling portion sizes and packing healthy foods when traveling.