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High BMI may increase the risk for many health problems. However, some studies show that slightly overweight people live longer, have reduced risk of dementia, and better tolerate the same health problems than those with normal weight.

With the growing number of overweight people around us, obesity is slowly but surely becoming socially acceptable. Nobody is surprised by rather fat models, singers and TV presenters anymore. In fact, many people argue that being a bit overweight, particularly after a certain age, is perfectly normal. Are they correct?

Some surprising recent scientific findings do fly in the face of classic medical concepts about the norms of body weight. It appears that a bit of fat can indeed bring some benefits, not only problems.

BMI As An Approximate Measure Of Health

Body mass index (BMI), also known as the Quetelet index, is a parameter indicating whether someone is at a normal weight, underweight, overweight, or obese. It measures weight in relation to the individual's height and gives a certain score. Depending on this score, a person is classified into one of four weight categories:

  1. Underweight: BMI below 18.5
  2. Normal weight: BMI of 18.5 to 24.9
  3. Overweight: BMI of 25 to 29.9
  4. Obesity: BMI of 30 or higher

Excessive BMI may increase the risks of many health problems, such as diabetes mellitus type 2, hypertension, angina pectoris, heart disease, heart and brain strokes, certain types of cancer, sleep apnea, kidney disease, osteoarthritis, fatty liver disease, pregnancy problems such as pregnancy hypertension and diabetes, and increased risk of cesarean delivery.

BMI measures should be taken with a bit of caution. 

For instance, professional athletes and bodybuilders in particular often appear to be overweight on the BMI scale. However, their higher BMI scores are linked to a higher muscular mass, rather than fat. So BMI is a measure more suitable for an “average Joe”.

How Does Body Fat Benefit Your Health?

However, recent studies have revealed that being slightly overweight may, in fact, improve a person's health and even lower their risk of mortality. Researchers discovered that an enzyme called nicotinamide phosphoribosyltransferase (NAMPT) secreted by the body's fat tissue controls the energy level in the brain and its response to a lack of food. They concluded that there may be an optimal amount of body fat for maximizing health and longevity. However, scientists still do not know what amount of fat is good, and how other body parameters play their role in conjunction with fat. Many studies reported that as we get older, people who are slightly overweight tend to have fewer health problems, especially a lower risk of dementia, and also a lower mortality rate.

Scientific findings point to the importance of NAMPT in producing a vital cellular energetic compound called Nicotinamide Adenine Dinucleotide (NAD), and in controlling the metabolism and aging processes. 

Scientists already knew that NAMPT enzymes play an essential role in producing energy inside the cell, but this new study suggests that this enzyme has important activities outside the cells in the blood circulation, and that this is actually a highly active and well regulated enzyme. 

Mouse studies have shown surprising results. Mice were raised with a deficit of NAMPT, and, as expected, the energy levels in their fat tissue were reduced. The effects on other tissues like liver and muscle were not significant, but there was a notable effect on the hypothalamus, an important part of the brain that plays a role in regulating body temperature, sleep cycles, heart rate, blood pressure, thirst and appetite. Low levels of NAMPT in fat tissue of mice resulted in low energy levels in the hypothalamus, and lower physical activity compared to mice without this defect.

Continue reading after recommendations

  • Shin-ichiro Imai (2009). Nicotinamide phosphoribosyltransferase (NAMPT): A link between NAD biology, metabolism, and diseases. Current Pharmaceutical Design 15(1): 20–28
  • Nawab Qizilbash, John Gregson, Michelle E Johnson et al. (2015). BMI and risk of dementia in two million people over two decades: a retrospective cohort study. The Lancet Diabetes and Endocrinology 3(6): 431–436
  • Flegal KM, Graubard BI, Williamson DF, Gail MH (2005). Excess deaths associated with underweight, overweight, and obesity. Journal of the American Medical Association 293(15):1861-7.
  • Photo courtesy of antiphase via Flickr:
  • Photo courtesy of Sjoerd Lammers street photography via Flickr:

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