MONDAY, Jan. 26, 2009 (HealthDay News) -- Eating less to remember more might become a new prescription for some elderly people, German researchers say.
They found that memory and thinking skills improved among healthy, overweight subjects who cut their calorie intake by 30 percent over a three-month period.
If further research supports this conclusion, "from a public health point of view, you could actually do something for the prevention of cognitive decline from aging," said lead researcher Dr. Agnes Floel, assistant professor of neurology at the University of Munster.
The study suggests that the calorie restriction may boost memory and cognition by reducing insulin resistance and inflammation, which may be linked to age-related cognitive decline. Improvements in memory could be especially important, the study added, because memory losses are an early indication of Alzheimer's disease and its precursor, mild cognitive impairment.
The research also tested whether a dietary increase in unsaturated fatty acids, such as the omega-3 fatty acids found in some fish, would yield similar benefits. Although these healthy fats have spurred better cognitive performance in rats, the new study failed to find a similar effect in humans.
The findings were expected to be published in the Jan. 27 online edition of the Proceedings of the National Academy of Sciences.
The 49 men and women in the study had a mean age of 60.5 years and a body mass index of 28. Body mass index is a measure of overweight and obesity, with overweight starting at a BMI of 25 and obesity at 30.
Those in the calorie-restriction group were not told what to eat but were advised to cut portions and not to eat less than 1,200 calories daily.
The calorie restrictors lost an average of five pounds, with those who most closely adhered to the dietary recommendations losing an average of eight pounds. This subset with the largest weight loss also showed the biggest improvements in memory performance, Floel noted.
Lona Sandon, a spokesperson for the American Dietetic Association, questioned whether the cognitive and memory improvements among those who restricted calories were the result of weight loss, rather than just cutting calories.
"With any weight loss, you'd expect the results they found," she said. "You'd expect better glucose, better insulin levels, and better C-reactive protein levels. C-reactive protein and high insulin levels are associated in other studies with high inflammation," Sandon explained. "You'd expect those metabolic changes with a small amount of weight loss."
Calorie restriction does have its drawbacks, however. According to Sandon, there's the danger that older people will not get adequate nutrition as they naturally begin to eat less in their early 60s. For that reason, it's important for people this age to maintain a healthy body weight, she said.
Floel, a neurologist, agreed that it is difficult to tease out whether the cognitive and memory improvements were a result of weight loss. "They always go together in a way," she said. Her research group plans additional studies trying to replicate their results in a larger population. Future study will also look at the correlation between calorie restriction and changes detected by MRI in the hippocampus and prefrontal cortex areas of the brain. The hippocampus deals with memory, and the prefrontal cortex controls executive functions and information retrieval strategies, she explained.
The benefits of dietary increases in unsaturated fatty acids also will be researched further, the team said. Floel's group will test whether the use of fatty acid-rich supplements such as fish oil can provide more accurate results than merely asking participants to improve their consumption, Floel added.
More information
There's more on maintaining a healthy weight at the U.S. Department of Health & Human Services.
