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Strickland: Are there any data on the pastoralist systems commonly found in Central Asia? Do you expect the composition of weight change at different BMIs to be the same across different populations?
Ferro-Luzzi: The pastoralists fall off the line: they have a very different diet from agriculturalists with much more protein. There is seasonality even in non-agricultural regions.
Kennedy: The index of seasonality you derived was based mainly on factors affecting agricultural production. In Kenya our first study was in a drought year, and when we did it again in a non-drought year, we did see swings but caused by different factors. With changing agricultural systems, e.g. irrigation, this will reduce the rainfall effect on crops but not the disease vector or other factors. Do you think your classifications may change if you look at the different forces affecting seasonality?
Ferro-Luzzi: We are suggesting a new system and the index could easily be adapted to changing conditions and local situations.
Prentice: I could help bring the Gambian data closer to your line because the data used were from the time of the sub-Sahelian drought in 1978. Now our seasonality is much smaller.
Durnin: What criteria did you use for a tolerable loss of fat-free mass? This could vary with the initial state of the body. Forbes' data on people losing weight started with their being obese. This is different from people losing weight when they already have very little fat.
Ferro-Luzzi: You are right, but the points on the graph refer to obese losing weight, normal people gaining and losing weight and anorectics gaining weight, including data of Forbes and Keys.
Norgan: The Forbes line used static difference data comparing big and small individuals and was not based on individuals' data. With high BMI do you have a higher delta weight loss?
Ferro-Luzzi: Yes, and those with a low BMI have a lower delta weight loss.
Waterlow: Jaya Henry has also looked at this and found the same as Forbes: the fatter you are, the more fat you lose. The N balances done on different levels of energy intake in the short term, losses are 2mgN for 1 kcal deficit. The figures for India are the same as America.
Naidu: Is there nutritional adaptation in the high seasonality areas? Are there nutritional dwarfs in these areas?
Ferro-Luzzi: Yes, in Ethiopia you can have both stunting and a low BMI; those with a lower BMI lose less weight.