Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health, leading to reduced life expectancy and/or increased health problems. People are considered obese when their body mass index (BMI),a measurement obtained by dividing a person's weight by the square of the person's height, exceeds 30 kg/m2, with the range 25-30 kg/m2 defined as overweight.
Sleep is the ‘most sedentary activity’, yet may be the only one that protects from weight gain. People today are experiencing 2 PARALLELTRENDS, INCREASING BODY MASS INDEX (BMI) AND A DECLINE IN AVERAGE SLEEPING TIME. OBESITY is reaching epidemic proportions throughout the developed world and is attributed largely to industrialization with reduced acute and chronic disease, increased food consumption, and lowered levels of physical activity. Early humans were likely to have gotten more sleep per night on average, since their circadian rhythms were more closely synchronized to the rising and setting of the sun. Today we have artificial light to extend our active phases and many other distractions that prevent us from getting adequate sleep.
According to recent estimates, the worldwide prevalence of obesity has doubled since 1980. This obesity epidemic has been paralleled in modern society by a trend of reduced sleep duration. Poor sleep quality, which is often associated with overall sleep loss, has also become a frequent complaint.
Growing evidence both from studies points to short sleep duration as a new risk factor for the development of obesity and its complications. Sleep is an important modulator of neuroendocrine function and glucose metabolism and sleep loss has been shown to result in metabolic and endocrine alterations,including decreased glucose tolerance and alteration of appetite regulating hormone.The relationship between sleep and obesity is likely mediated by multiple pathways.
An up-regulation of the activity of orexin neurons and changes in appetite-regulating hormones may affect food intake.
It has been previously shown that ghrelin, a hormone promoting hunger, increases with sleep restriction, whereas leptin, a hormone contributing to satiety perception, decreases.
If a person is overweight and suffering from sleep-disordered breathing, he/she may not be as motivated to exercise or to diet. When apnea leads to daytime sleepiness, it may be that much harder to begin or sustain an exercise program, which has been shown to help people begin or maintain weight loss. Sleep deprivation appears to be a risk factor for obesity, the sleep fragmentation, overall sleep loss, and daytime sleepiness associated with OSA could similarly favor weight gain, which then further worsens OSA. Severe obesity appears to be associated with marked sleep disturbances, even in individuals who do not have OSA.
Such sleep disturbances may equally predispose severely obese individuals to accumulate a sleep debt and may contribute to the dysregulation of appetite, limit the drive for physical activity, and further compromise weight maintenance through a weight loss diet. Successful treatment of sleep apnea, usually with nasal continuous positive airway pressure (CPAP), may reduce sleepiness and then motivate patients to effectively lose weight, which will in turn help the obesity and the sleep apnea. Most experts say as little as a 10% decrease in weight can lead to significant clinical improvement in the severity of sleep apnea. However, in the more severe cases of apnea, CPAP is a necessary first step to better sleep and feeling motivated to embark on a weight loss program.