Low body mass index, physical work capacity and physical activity levels.

In a normal population the distribution of body mass index (BMI) is such that a certain proportion of the population is likely to be at low values without necessarily being malnourished. However, although they may have low BMIs without being malnourished, they could certainly be physiologically and physically disadvantaged. An attempt is made to dissect out the probability of work capacity and physical activity being influenced by changes occurring in the human body with diminishing BMI. The conclusion reached is therefore that before physical activity is affected, the BMI would probably have to be 17 or less, although it is possible that work capacity might be reduced before this level is reached. In any case, work requiring the use of the body mass - such as carrying loads, digging or shovelling earth or coal, pulling or cycling a rickshaw, stone splitting etc.- would impose a greater stress on people of low BMI.