We’re sure you’re all familiar with the stereotype of the “fat American.” Unfortunately, there’s some truth behind it. The obesity statistics in this country are nothing short of frightening.
A person is considered overweight if they have a body mass index (BMI) of 25-29.9, while obesity is classified as a BMI of 30 or greater. If you’re not familiar with it, BMI is a measure of body fat based on height and weight. (To find out if your BMI is in a healthy range, try the BMI calculator on the National Institute of Health’s website.)
According to the Centers for Disease Control and Prevention (CDC), two-thirds of U.S. adults are overweight or obese, putting them at a much higher risk for health problems including cardiovascular disease, diabetes and certain types of cancer. With so many Americans at an unhealthy weight, it’s fair to say we’re in the midst of an obesity epidemic.
While diet and exercise play a large role in weight management, research has been done to evaluate other factors that may affect your weight, from sleep to mental state to things as seemingly obscure as how much bright light you are exposed to before bedtime.
Along these lines, a new study published in the International Journal of Obesity focused on sleep, screen time (i.e., time spent in front of the TV or computer), depression and stress, to see whether they could predict success in a weight loss program.
Why these lifestyle factors?
Sleep: A number of studies have looked at the inverse relationship between the amount of sleep a person gets and levels of hormones that may contribute to weight gain. The study authors cite previous research that shows decreased levels of leptin and increased levels of ghrelin, which are positively associated with satiety and hunger, respectively.
Screen Time: It’s hardly a surprise that studies have found that a greater amount of time spent in front of the television has been associated with higher BMI and percentage body fat, and lower levels of physical activity. It has also been demonstrated that people who spent 11 or more hours per week on the computer were at higher risk for obesity, as well as gaining weight back after losing it.
Depression and Stress: Both depression and stress have been associated with obesity. In particular, obesity was found to increase risk for depression, and depression was predictive of becoming obese. And studies suggest that chronic stress leads to an increased intake of energy- and nutrient-dense foods in both animals and human, thus leading to obesity. Furthermore, chronic stress may activate the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, causing weight gain and related health problems, according to two recent reviews.
In this particular study, researchers wanted to look at the above factors in the context of an intensive weight loss intervention program. This was a two-part study. Phase I involved 472 adults who enrolled in a six-month weight loss program:
- Mean age: 55 years (25 percent of participants were over 65)
- Mean BMI: 37.7
- Eighty-three percent women
Success was measured by a weight loss of at least 10 pounds, which was required for admission into the Phase II maintenance portion of the trial (results still pending).
The weight loss intervention consisted of 22 group sessions led by nutrition and behavioral counselors over a six-month period in which participants were given the following goals:
- Reduce calorie intake by 500 calories per day to lose 0.5 to 2 pounds each week.
- Eat a healthy, low-fat diet rich in fruits and vegetables.
- Exercise at moderate intensity most days, adding time little by little until you are exercising 30-60 minutes every day and at least 180 minutes each week.
- Record everything you eat and drink every day.
- Record your minutes of exercise every day.
- Set short-term goals and create action plans to reach those goals.
- Attend all group sessions.
In addition to the goals above, the study authors set out to address the following three questions:
1. Do measures of sleep time, insomnia and screen time at entry predict success in a weight loss program? Do measures of depression and stress add to this?
2. Do changes in sleep time, insomnia, screen time, depression and stress correlate with weight loss?
3. Do associations between weight loss, session attendance, exercise minutes and food records in this study population replicate those previously documented in the literature?
At the end of six months, the average weight loss for the group was 13.9 pounds, and 60% of participants lost 10 pounds or more making them eligible for the second phase of the study.
And here are the highlights of what researchers came up with in regard to the above questions:
“We found that entry sleep time predicted success in the weight loss program. Specifically, participants sleeping [less than or equal to] 6h or [greater than or equal to] 8h daily were less likely to achieve eligibility for Phase II than those sleeping [greater than or equal to] 6h and [less than or equal to] 8h a day. In addition, entry stress (PSS) score predicted both eligibility for Phase II and actual weight loss. ”
Furthermore, people who said they got less than six hours of sleep a day and reported the highest stress scores at the start of the study were about half as likely to lose the 10-pound minimum as those sleeping between six and eight hours a day with a low stress score.
Interestingly, in this study, screen time did not predict success in the weight loss program or change in association with weight loss. However, the amount of time spent exercising is obviously highly correlated with weight loss, so you could infer that more time parked on your butt is not going to help your cause if you’re looking to shed unwanted pounds.
Change in stress levels, on the other hand, did correlate with change in weight during the program. And, as we mentioned earlier, chronic stress may play a role in bad eating habits and hormonal responses that can cause a person to gain weight.
So, if you are struggling to lose weight, or keep it off, this study suggests that getting between six and eight hours of sleep each night will help. Additionally, finding ways to cope with stress (other than eating) may aid your progress, and getting fit should help reduce your stress level.
 Elder CR, Gullion CM, Funk KL, DeBar LL, Lindberg NM and Stevens VJ. Impact of sleep, screen time, depression and stress on weight change in the intensive weight loss phase of the LIFE study. International Journal of Obesity [epub ahead of print] 29 March 2011; 1–7.