A study on appetite control in the over-80 demographic might provide clues on how to control appetite in younger folks. Dr. Mary Hickson from Plymouth University in Plymouth, UK, and colleagues published a preliminary study in the journal Appetite that examined hormonal factors known to affect eating behavior.
The inspiration for the study was the observation that many older people suffer from what has been termed "aging anorexia," or a loss of appetite that isn't linked to any particular ailment. This can, of course, lead to malnutrition and compromise health. Indeed, the authors cite data indicating that in the United States, "the rate of malnutrition mortality for all adults was 0.8 per 100,000 people, but for 75-84 years it was 5.2, and for over 85 years it was 20.9."
To investigate this phenomenon, the authors examined the levels of and responses to several gastrointestinal hormones that are involved in appetite and feeding control.
The hormones they investigated included:
- Ghrelin: the so-called hunger hormone, is secreted in the GI tract when the stomach is empty. Causes an increase in hunger and physiological changes to deal with food intake.
- Acyl.-ghrelin: activated form of ghrelin
- GLP-1:glucagon-like peptide: when glucose levels in the blood rise, GLP-1 induces the pancreas to release insulin and thus promote normal glucose levels.
- PYY: Peptide YY is released in response to feeding and reduces appetite.
It was difficult for the investigators to recruit people in the older age groups who were healthy — and not on medications that might interfere with the study. They ended up with a total of 31 volunteers, ranging in age from 20 to 92 — but only 6 (all women) were over 80 years. Individuals over 80 years of age had somewhat different body compositions than did younger groups — they had slightly higher body fat and lower lean body mass percentages.
Each person gave a fasting blood sample, and another after a nutritionally complete liquid meal. For the next 3 hours they gave additional blood samples and completed tests related to sensations of appetite. When 3 hours were up, they were presented with an excess of a second test meal (women only), and told to eat as much as they wanted.
Analysis of the hormonal levels in the women in each age group showed that, compared to the 60-79 age group, the 80+ group demonstrated a higher level of PYY than did any other age group. There were no other significant differences in any of the other hormones tested. Further, this group consumed fewer calories from the second meal than did any other age group (416 vs over 680 for the other groups). The data on appetite revealed that the older groups had significantly less hunger than the younger ones, thus explaining the decreased energy intake.
Thus, the authors concluded "Our data suggest that there may be an increase in the concentration of PYY after meals with healthy aging in females, potentially resulting in a reduced appetite."
Clearly, much more work must be done to test this conclusion — this was a very small study, and only women were participants in the oldest group. However, if it is replicated, perhaps exogenous PYY might be a means of helping to control appetite and overeating in other populations.