Busy days often turn into busy nights and, for some families, it can be eight o'clock by the time dinner is served. Does eating this late, or later, affect your body weight? Researchers have been debating this for several years and new research published in the journal, Obesity, supports the idea that eating after 8pm may indeed be associated with a higher Body Mass Index (BMI), a measurement of weight for height.

In the small study, researchers followed the sleeping and eating patterns of 52 people over seven days. These participants were divided into two groups depending on their sleep habits. They were classified as "normal sleepers" if the midpoint of their sleep cycles was before 5:30am. If a participant's sleep cycle midpoint was after 5:30am they were classified as a "late sleeper".

When these sleep patterns were compared to the participants' eating habits, the researches found that the "late sleepers" ate more calories at dinner time and after, and ate fewer fruits and vegetables overall. The researchers also found that the late sleepers slept fewer hours overall and had higher BMI compared to those who were "normal sleepers". Even after statistically adjusting for factors such as hours slept and fruit and vegetable intake, it was found that eating after 8pm (meals and/or snacks) was associated with a higher BMI.

Bottom Line: Lack of sleep has long been associated with weight gain. Now there is research to support that eating later at night (when you should be sleeping) also likely means that you will weigh more. Try to slowly adjust your sleep patterns to allow you to follow the pattern of sunrise and sunset; falling asleep a few hours after the former and rising with the latter. In addition to regular physical activity and a healthful diet, adequate sleep and taking in most of your calories before 8pm may also help you to maintain a healthy weight.

Source: Obesity , (28 April 2011) | doi:10.1038/oby.2011.100

Say Goodbye to BMI?

However, the BMI calculation is not perfect. BMI only takes height and weight into consideration, not muscle mass versus fat mass. This means, for example, that two men can have the same BMI, but very different health status. Imagine two men who are both six feet tall and weigh 250 pounds. One is a couch potato with a passion for pizza and the other is a professional hockey player, a Stanley Cup winning, Boston Bruin, for instance. They both have a BMI of 30.5 which places them in the category of "obese". While this classification may hold true for the couch potato, the hockey player is hardly a person who needs to lose weight.

While BMI can give you an idea of where you stand in relation to a healthy weight, most health professionals agree that there needs to be a more accurate and simple assessment of body fatness. To that end, researchers in California recently published a paper reporting that they have determined a more accurate way of assessing body fatness. This new formula is called the body adiposity index and is calculated using height in meters and waist circumference at its widest point in centimeters (BAI = ((hip circumference)/((height)^1.5)-18)). This formula was developed then validated against the gold standard of body fat analysis, dual-energy X-ray absorptiometry (DXA) and was found to be an accurate predictor of body fatness.

Bottom Line: If you're interested in determining your own BAI and don't want to tackle that daunting equation above, click here. While an alternative method to BMI is needed, this calculation may also need to be refined. Researchers only looked at Mexican and Black populations in the US, so more research needs to be done to see if this equation is appropriate for other minorities and whites, as well.  

Source: Obesity 19, 1083-1089 (May 2011) | doi:10.1038/oby.2011.38

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