Association between weight gain, obesity and sleep duration

I suppose we have all heard lot of the saying that sleep duration strongly affects our weight and health. And according to a study, both short and long sleep hours are indicators to predict an increased risk for future health (Science Daily, 2008), and there are a lot of controversies out there nowadays regarding this topic. Therefore, in order to explore it further, I will be gladly introducing the research study called association between weight gain, obesity and sleep duration on a large-scale 3-year cohort study, done by St. Luke’s International Hospital in Tokyo.   

So basically, Kobayashi D., Takahashi O., Deshpande G., Shimbo T.& Fukui T. (2011) performed this retrospective study that surveyed 21,469 healthy individuals who were 20 years or older who had annual health checkups at St. Luke’s between 2005 and 2008. And the purpose of attracting all these apparently healthy citizens was to promote early detection of any chronic diseases (Kobayashi D. et al, 2011). Also, questionnaire about their average of sleeping time per night were filled out. In addition, statistical measures were used in conducting the research. For instance, the responses were analyzed using descriptive statistics like mean and standard deviation. As well as regression analysis which was used to explore the relationship between sleep duration, age, gender, past medical history, and level of physical activity (Kobayashi D. et al, 2011).

The study had found that those who slept for 7 hours are less likely to come obese than those who slept for 5 hours or less. And to contrast, individuals who slept more than 8 hours had no huge difference comparing to the 7-hour-sleepers in terms of their body mass index, but have a tendency to become obese in the future (Kobayashi D. et al, 2011). The result was interesting because it was not like the longer we sleep, the less likely we will be obese, but instead, more than 8 hours of sleep will contribute to increasing chances of weight gain or new-onset obesity.

As for the conclusion, the findings of this research study suggest that the optimal sleep hour for a healthy weight is around 7 hours per day. Additionally, sleeping less than 5 hours results in both weight gain and increasing potential risk of obesity for both males and females (Kobayashi D. et al, 2011). However, this study may be biased in the sense that the data collected is only from people who are healthy and coming to annual check-ups with this specific hospital. Thus, this sample does not represent the overall population. Other limitations might be that the questionnaires used did not incorporate information on quality or satisfaction of sleep. Also, it is a retrospective research, which means that larger sample size and perspective method will be needed to support the results.

I guess after knowing this fact, I will stick with sleeping 7 hours every day. Will you?

References:
Kobayashi D., Takahashi O., Deshpande G., Shimbo T.& Fukui T.(2011). Association between weight gain, obesity and sleep duration: a large-scale 3-year cohort study. Sleep and Breathing. 1-5 

Science Daily, 2008. Short, Long Sleep Duration Is Associated With Future Weight Gain In Adults. Retrieved from http://www.sciencedaily.com/releases/2008/04/080401081932.htm

Is BMI Appropriate for Assessing Health?

When it comes down to the topic of contemporary health, controversies arise continuously and many of them never settle. Thus, it is our responsibility to pick a side that makes more sense and look for appropriate evidence to support it. And most importantly, stay with that side of the argument. Today, I came across an interesting controversy in the field of healthy weight, which is also the title of this blog: Is BMI appropriate for assessing health? Just a brief explanation to those of you who do not know, BMI is the Body Mass Index that is used to calculate the ratio of our weight and squared height, in kilograms and meters respectively.

One side of the controversy is that the BMI is the appropriate measure because it is what our Canadian health system uses for determining whether we are at health risk or not. In addition, it is an inexpensive and easy method of classifying the weight groups and identifying our weight status. (Centers for Disease Control and Prevention, 2011) And the following image is about the division of BMIs:

The other side of the argument is that BMI does not take into consideration of the body composition, and it also has several limitations. First of all, for muscular adults, they tend to have a BMI in the overweight range and over look the health risks due to the large amount of muscle tissue they have. Secondly, young adults who have not achieved their full growth and those who naturally have a very lean body may not be as dangerous as the BMI indicates. Last but not the least, seniors over the age of 65 needs special attention because the normal range for them could differ from younger adults. (Health Canada, 2005)

As for my opinion, I agree with the second idea, where BMI is not too appropriate in accessing health. As for me, I have a BMI of 19.5 where as you can see, according to the chart above, I fall under the normal category. However, BMI was introduced in the early 19th century by Lambert Quetelet, who was a mathematician, not a physician. He produced this formula to get quick measures to assist the government in allocating resources. (NPR, 2009) Personally, I am more concerned about my abdominal fat, and also fat stored at other parts of my body. Therefore, I would like to know more about my body composition instead of just knowing that I am normal comparing to the overall population, and having no consideration of any health risk I might experience. It is researched by scientists at the Mayo Clinic (as cited in Rachel B., 2011) that after comparing thousands of BMIs, it is found out that more than half of the people with normal BMIs actually had the same risks of chronic illness as those who had high BMIs due to high body fat percentage, which has another interesting name, "skinny fat".

So, I believe that we should not be lulled into a false sense of security although our BMI falls in the normal range. Instead, we need to take into account of other measures as well.  For instance, the waist circumference, it is an indicator of abdominal fat (Health Canada, 2005) and the body composition test that gives us the accurate fat percentage so we can assess our health better and maintain a healthy weight as we move on.

References:

Centers for Disease Control and Prevention (2011, September 13). About BMI for Adults. Retrieved from http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html

Health Canada (2005, August 10). Canadian Guidelines for Body Weight Classification in Adults. Retrieved from http://www.hc-sc.gc.ca/fn-an/nutrition/weights-poids/guide-ld-adult/qa-qr-pub-eng.php#1

NPR (2009, July 4). Top 10 Reasons Why the BMI is Bogus Retrieved from http://www.npr.org/templates/story/story.php?storyId=106268439

Rachel B (2010, March 29). Mayo Clinic Study Reveals Many Thin People Are Actually Obese. Retrieved from http://voices.yahoo.com/mayo-clinic-study-reveals-many-thin-5720710.html?cat=5