Obesity is increasingly becoming a worldwide health problem and its strong involvement with SDB is causing concern, cases of SDB will continue to rise and control measures such as weight control by public health and clinical procedures are of equal importance in this aspect. These realizations are of importance and have clinical implications for overweight patients with moderate and mild SDB who tend to be poor candidates for nasal continues positive airway pressure therapy (nPAP). It is considered that weight loss may be the appropriate strategy to reduce severity and advancement of SDB and daytime improvement symptoms, More over people who have not been diagnosed with SDB and are overweight will find it important to lose weight or at least not gain it.(E Peppard Paul et al). Our findings over the last ten or so years there has been an increase in the number of over weight individuals Being over weight is a common medical occurrence and is realized in more than 60% of the reffered patients for a diagnostic sleep evaluation. Epidemiologic surveys from all around the globe have consistently realized that body weight is the biggest risk factor for OSA. In the WSCS (Wisconsin Sleep Cohort study), difference in body mass index (BMI) was linked with an increase in disease prevalence. Other community based and population studies conducted around the world in the confirmed that excess body weight is substantially correlated with a graded increase in obstructive sleep apnea occurrence. Moreover, studies from WSCS Wisconsin Sleep Cohort Study, and the Cleveland Family Study showed that increase in body weight with time certainly accelerated the progress of OSA or lead to occurrence of moderate to severe. Supporting the available body of observational data are studies on the effects of dietary or surgical weight loss which show that reducing severe obstructive sleep apnea is possible with a reduced body weight. However strictly, small study samples, lack of appropriate control groups, the invariable observation is that weight loss, can improve the reduction of obstructive sleep apnoea various patients and may be completely viewed to be the best remedy for some patients. despite all this there is increased controversies as whether specific measures such of body habitus such as neck circumference and waist circumference that reflect a central versus peripheral distribution of fat are associated with an increased risk for OSA .Determining such measures of central obesity are able to adequately predict OSA can be severe or there is a risk. However analysis from the Sleep Heart Health Study data indicate that in older and middle aged middle-aged, moderate to severe obstructive sleep apnea, is defined as according to polysomnographic readings to be or equal to 15 occurrences per hour which is independent of BMI, waist circumference and neck circumference. body weight increase is found to alter upper airway mechanism while sleeping though several mechanisms that include:

(1) Alterations in neural compensatory mechanisms that maintain airway potency.

(2) Respiratory control system instability, and

(4) Reduction in functional residual capacity with a resultant decrease in the stabilizing caudal traction on the upper airway.