A new study suggests that our instinctive "nutritional wisdom" fails when unhealthy food choices are more available than healthier nutrients.
Research carried out on rodents show that when presented with variety, animals have a tendency to select the wrong kinds of nutrients.
While previous tests have proved that there is a natural disposition to select a balanced diet with all necessary nutrients and suitable for the respective environment, the growing obesity rates in the US and developed prompted research to find out what disrupted the natural behaviour.
Michael G. Tordoff from the Monell Chemical Senses Center, Philadelphia, US, reported on his findings in the current edition of The American Journal of Physiology. He is also the author of "Obesity by choice: the powerful influence of nutrient availability on nutrient intake."
In his study, Tordoff found that most rats given a choice from separate sources of protein, carbohydrate, and fat thrived if given one cup of each but half failed to thrive if given one cup of each and three extra cups of carbohydrate or fat. Rats given five bottles of sucrose solution and one bottle of water became fatter than rats given five bottles of water and one of sucrose.
These studies may point to a model for human obesity, suggested the author, in which the availability of the wrong food can override physiological controls of ingestion.
The results reveal that the more sources of a nutrient a rat has, the more it chooses to eat. The effect of nutrient availability is so powerful it overrides the healthy physiological controls of food intake.
The author said that the study shows the need for the concept of "nutritional wisdom" to be re-examined because previous studies do not consider when multiple choices of each nutrient are available.
He also argues that simply providing multiple sources of food stimulates intake and thus may contribute to, and in some cases account for, the variety effect. Availability of food, and not the physiological actions of the body, could be more important in controlling obesity, suggests the study.