The NIA monkeys ate naturally sourced foods and the UW — Madison monkeys, part of the colony at the Wisconsin National Primate Research Center, ate processed food with higher sugar content.
In contrast,
the NIA monkeys were fed according to a standardized food intake chart designed by the National Academy of Science.
Further, the WNPRC control group probably ate more overall, because their meals were unlimited, whereas
NIA monkeys were fed fixed amounts.
Genetics probably explains part of the variation between the monkey studies, too, as
the NIA monkeys were descended from lines from India and China, whereas the Wisconsin monkeys were all from India.
Not exact matches
The WNPRC
monkeys» diets contained 28.5 % sucrose, compared with 3.9 % sucrose at the
NIA.
As adults, control
monkeys in the WNPRC study weighed more than their
NIA counterparts.
An influential 2012 report on 120
monkeys being studied at the National Institute of Aging (
NIA) reported no differences in survival for caloric restriction animals and a trend toward improved health that did not reach statistical significance.
Ricki Colman, a senior scientist at the Wisconsin Primate Center, who presently co-leads the project, suggests that
NIA's control
monkeys were actually calorie - restricted.
Even so, in the
NIA trial, four of the
monkeys that began the diet as adults lived to be over 40, breaking all known records for macaques — an observation which may cheer those who practise calorie restriction.
The previously reported lack of difference in survival between control and restricted groups for older - onset
monkeys within
NIA emerges as beneficial differences when compared to the UW — Madison data.
In two
NIA studies, healthy, normal - weight rhesus
monkeys were placed on long - term calorie restricted regimens.
A comparison of body weight of control animals from both studies with each other, and against data collected in a multi-centred relational database of primate ageing, suggests that the
NIA control
monkeys were effectively undergoing CR.
These data contrast with observations in the 2012
NIA intramural study report, where a difference in survival was not detected between control - fed and CR
monkeys.