Scientists from The University of Pennsylvania have decided to check whether sleep time and the number of sleep hours are an additional factor predisposing to putting on weight. Researchers were interested not only in the relationship between the amount of sleep and objectively measured body weight, but also in the relationship between the amount of calories intake and the time of meal consumption which considerably contributes to gaining weight.
According to World Health Organisation, obesity is abnormal or excessive accumulation of fat tissue which can negatively influence health. BMI (Body Mass Index) is simple, but not totally precise, indicator used in obesity diagnosis. The result in the range of 25-30 means overweight and above 30 is considered as obesity.
WHO claims that every year 2,8 mln of adult people die because of overweight and obesity what is fifth, in terms of frequency, risk factor of death in the world. About 10% of adults of the world population is involved in the phenomena. More than 40% of children under 5 years old are obese. High BMI is one of the main risk factors of cardiovascular diseases, diabetes, osteoarticular system disorders and in particular predisposes to degenerative changes and tumours of breast, large intestine or endometrial.
According to WHO the main causes of obesity are excessive intake of high-calorie meals and inadequate physical activity in relation to amount of eaten calories. Not only changes in the society, but also in the environment have an influence on the decrease of physical activity. Easiest access to high-calorie products, sedentary life style, or using the means of transportation is not without negative influence on body weight increase.
The scientists in order to verify the thesis about negative influence of small amount of sleep on the body weight subjected 225 persons between 22-50 years old with BMI indicator 25.0± 3.1 to the research for 18 days. Research (n=198) and control (n=27) groups were created. Additionally, in the research group after two nights (when the number of sleep hours was 10-12h) the number of hours was limited to 4 for the next 5 nights. Then members of this group returned to the normal number of sleep hours. During the research meals were served regularly, however, people who took part in the study had access to unlimited additional food. Control group was subjected to the same conditions except for sleep hours which number was 10 (10 p.m. to 8 a.m.).
Analysis of the results brought many vital correlations. In the time of the first 3 days when the hours of sleep were limited the amount of eaten fats, carbohydrates and proteins increased while in the fourth day fat intake was significantly different in comparison with days of normal sleep hours in the control group.
Also, the difference concerning gaining on weight appeared. That means the increase of BMI indicator in relation to the race and sex of researched people. Afro-Americans gained weight faster than people of Caucasian race. It was noticed that men put on weight faster than women. Summing up, the group which is at highest risk of BMI increase are male Afro-Americans. Tendency to sleep less than 6 per 24 hours in people of this race may only intensify this correlation.
Above research have show that the plan of body mass reduction should contain not only appropriate calories number, but also proper sleep amount. Further research should focus on the search for causes which influence divergence in the area of body weight increase in people of different sex and race who live in the same conditions.
Written by: Maciej Jakuszko, Sylwia Romanowska, Karolina Gasińska, Jerzy Bednarski
Source:
1)Effects of Experimental Sleep Restriction on Weight Gain, Caloric Intake, and Meal Timing in Healthy Adults.
Spaeth AM, Dinges DF, Goel N. http://www.ncbi.nlm.nih.gov/pubmed/23814334
2) http://www.who.int/mediacentre/factsheets/fs311/en/
3)Knutson KL, Van Cauter E, Rathouz PJ, DeLeire T, Lauderdale DS.Trends in the prevalence of short sleepers in the USA: 1975-2006. Sleep 2010;33:37-45.
4)Lauderdale DS, Knutson KL, Yan LL, et al. Objectively measured sleep characteristics among early-middle-aged adults: the CARDIA study. AmJ Epidemiol 2006;164:5-16.
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