Objective
To train adults to recognize symptoms of glycemia using emerging feelings of depletion (i.e. bearable hunger). Design: within-individual verification of the learned ability.

Setting
University Hospital, tertiary care.

Subjects
60 healthy adults (24 males and 36 females, aged 15-60), all of whom had functional complaints or were overweight, were prepared by primary or secondary care before the experiment began.

Methods
Rather than preventing and ignoring energy depletion, the subjects in this experiment waited for feelings of depletion to emerge and then measured their level of glycemia, thereby training them to recognize the association between the two. By repeating this process at the same blood glucose level, most learned how to make the association within two weeks. Thereafter, they took meals whenever they recognized the onset of feelings associated with this level of glycemia. Moreover, they were able to adapt their meal intake to provoke the emergence of the same depletion feelings at the desired meal time for 80% of meals. This was made possible by matching dietary intake with presumed inter-meal expenditure, and by consuming copious amounts of fruit and vegetables.

Two months later, at a verification session in the hospital laboratory after an overnight fast, subjects declared whether or not they perceived depletion feelings. They also predicted their current blood glucose level. A venous blood sample was taken for analysis, using the hexokinase method and hospital autoanalyzer. Subjects were also asked whether they thought they could continue the programme in the long term.

Results
66 of 71 eligible subjects came to the verification session after two months. Six of these were excluded due to illness. Of the remaining 60 subjects, 25 were at that moment perceiving depletion feelings and had glycemia levels measuring an average of 3.98 mmol/l (range: 3.75-4.21, ± 2SD). Those who did not perceive depletion feelings at that moment (35 subjects) had significantly higher levels of glycemia, measuring an average of 4.90 mmol/l (4.74-5.06, ± 2SD).

Under 'normal' circumstances (i.e. ignoring their individual condition), the levels of glycemia recorded (range: 3.1-5.7mmol/l) would have allowed ad libitum intake in the entire group of 60 subjects. Instead, by waiting for feelings of depletion, the subjects in this experiment ensured that they ate only at the lower end of the range of preprandial glycaemia. Moreover, 80% of subjects thought that they would easily be able to continue to use this intake method in the very long term.

Conclusion
Feelings of depletion emerge as a highly reliable threshold for predicting glycemia between 4.6 mmol/l and 3.1 mmol/l in trained adults, thereby indicating the latest time at which a meal should be consumed to prevent overeating.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

© 2002 Noldus Information Technology bv