The results of a recent study indicate that sleep quality can influence whether or not weight loss is achieved through a loss of fat or of lean body mass.
The research was performed by the University of Chicago and was led by Dr. Plamen Penev; the entire study is currently published in the Annals of Internal Medicine’s October 5th issue.

Study Details

For the study, researchers found 10 overweight men and women and had them live in a sleep lab for two, 2-week sessions.
 
During one session, participants got 8.5 hours of sleep per night, while they only got 5.5 hours in the second session.   During both two- week intervals, subjects were put on a low calorie diet.
Although the weight loss in terms of pounds was virtually the same during both sessions, the difference was the “type” of weight that was lost.  During the 8.5 hour per night session, participants lost an average of 3.1 lbs of fat and 3.3 pounds of fat free or lean body mass.
  
During the shorter sleep duration, on the other hand, both men and women lost an average of 1.3 lbs of fat versus 5.3 pounds of lean body mass. 

Dr. Penev, who is an associate professor of medicine at the University, tells WebMd that the lack of sleep makes the body “stingier when it comes to using fat as a fuel.”

In addition to the difference in weight loss type, the participants reported they felt “hungrier” at night when they were sleep deprived.
 
It turns out there is a chemical explanation for this.  The researchers discovered that levels of the appetite hormone ghrelin were higher among the subjects during the shorter sleep session than in the longer two-week period.  Specifically, blood levels of ghrelin were 75 nanograms and 84 ng/L, respectively.

Although Dr. Penev clearly demonstrated a link between sleep duration and fat loss, he concedes that the research was limited for several reasons:

*the pool of participants was small
*he is unsure how well a sleep lab environment mimics the “real world”
*the study focused on short-term weight loss only

He tells Reuters that more research will need to be done to determine the long-term effects of sleep deprivation and weight loss.

Advantages of Cardio

In reference to the above mentioned study, Michael Brues, PhD and director of the sleep division for Arrowhead Health in Glendale, AZ was quoted by WebMd as saying that sleep hygiene,  such as avoiding caffeine after 2:30 pm and engaging in an exercise routine, can significantly enhance sleep quality.

His assertion confirms the results of a recent study funded by the National Institute on Aging that demonstrated the positive effects of cardio exercise routines on sleep quality. 

Dr. Phyllis Zee led a team of researchers from Northwestern University in Chicago that recruited a group of 23 formerly sedentary individuals; most of them were women aged 55 and older.

The participants engaged in a cardio routine for 16 weeks by either walking on a treadmill or riding a stationary bicycle.  At the end of the study, they all reported that on average, sleep quality improved over the duration. 

Reuters reports that according to Dr. Zee, 25% of the American population suffers from insomnia; this percentage can increase to up to 40% in older adults.