An unhealthy weight can affect a person's well-being in various ways. That is why many people make a conscious effort to lose excess body weight. But, it turns out that a hidden factor — sleeping patterns — could easily thwart these efforts. An unhealthy weight, however, is not the only problem that threatens the well-being of people in the U.S. and elsewhere. Lack of good quality sleep also causes problems for people around the world. In the current research, Prof. Salas-Salvadó and colleagues analyzed the medical data of 1,986 individuals with a mean age of 65 years over the course of a year. All of these participants were overweight or had obesity at baseline, and they also had metabolic syndrome, a cluster of health risk factors that include high blood pressure (hypertension), increased levels of insulin (hyperinsulinemia), low glucose tolerance, and abnormal levels of blood lipids (dyslipidemia). At the end of the study period, Prof. Salas-Salvadó and team found that the participants who, at baseline, reported not sleeping for the same number of hours every night — a phenomenon called high sleep variability — had lost less weight after a year than those who reported a regular sleep pattern; they also experienced less of a reduction in body mass index (BMI). "The findings of our study highlight the importance of sleep characteristics on weight and adiposity responses to lifestyle intervention programs in elders with metabolic syndrome," the researchers conclude.