COGNITIVE EFFECTS OF A LONG-TERM WEIGHT REDUCING DIET

Authors: Kretsch, Mary; GREEN, MICHAEL - INSTITUTE FOOD RES UK; Fong, Alice; ELLIMAN, NICOLA - INSTITUTE FOOD RES UK; JOHNSON, HERMAN - 5330-07-00

Submitted to: International Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Recent research has shown that "cutting calories" to lose weight can impair mental performance in women. Specifically, dieting women have been found to have lower ability to sustain attention, poorer short-term memory, and longer reaction times than non-dieting women. These findings have important implications for the treatment of obesity. However because the previous studies relied upon self-reports of dieting from the women, we decided to examine this concern under carefully controlled conditions. Thus, we studied whether or not limiting calories for 15 weeks would adversely affect the mental performance of childbearing age, overweight women. Tests were used to measure a woman's ability to sustain and focus attention, short-term memory, reaction time and motor performance (i.e. two finger tapping speed). For the 15 weeks, calories were limited to 50% of that required to maintain the original body weight of each woman. The women lost an average of 27 pounds of body weight, most of which was fat. Simple reaction time significantly slowed during dieting and did not readily reverse to normal after dieting. In contrast to the previous short-term dieting studies, sustained attention and short-term memory were not impaired with controlled, long-term dieting. Whether or not the slowing of reaction time found with dieting is great enough to increase susceptibility to accidents is not known. This and other practical, as well as biological, consequences of reaction time slowing with dieting warrants further study.

Technical Abstract: Objective: Does long -term caloric restriciton adversely affect cognitive function? Design: Subjects were healthy, premenopausal obese women (experimental group: n=14, control group: n=11). Longitudinal study (repeated measures within-subject design) comprised of three periods: baseline (3 wk), 50% caloric restriction (15 wk) and weight stabilization (3 wk). Measurements: A standardized computerized test battery used to measure multiple aspects of cognitive function: sustained attention, immediate memory, simple reaction time, motor performance and attentional focus. Height, body weight, and body composition were also measured. Results: Dieting women lost 12.3+/-5.5 kg (mean +/- SD) of body weight, most of which was fat. Simple reaction time slowed significantly but did not diminish the sustained attention, motor performance or immediated memory of the dieting women. Word recall performance significantly improved dby 24% at the end of caloric restriction and was significantly correlated with the amount of body weight lost during the early weeks of caloric restriction and with anxiety level the last week of caloric restriction. Word recall performance returned to baseline with restoration of sufficient calories but simple reaction time did not readily reverse. Conclusions: The slowing of simple reaction time is a short-term and long-term consequence of caloric restriction which does not readily reverse upon restoration of sufficient calories. In contrast to previous short-term dieting studies, sustained attention and immediate memory were not impaired with caloric restriciton. Further research to assess the physiological and practical consequences of simple reaction time slowing with dieting is warranted.