Effect of an acute fast on energy compensation and feeding behaviour in lean men and women.
OBJECTIVE
Humans appear to defend against energy deficit to a greater extent than energy surplus. Severe dietary energy restriction resulting in 5-30% weight loss often leads to hyperphagia and weight regain in lean subjects. However, the period of time over which fasting is often endured in Western society are far shorter, approximately 1-2 days. This study examined how a 36 h fast effected the subsequent day's energy and nutrient intake in a group of 24 healthy, lean men and women.


METHODS
Subjects underwent two 2 day treatments, termed 'fast' and 'maintenance'. During the 'fast' treatment, subjects were fed a maintenance diet on the day prior to the fast (day -1) to prevent overeating. They then consumed non-energy drinks only, from 20:00 h on day -1 to 08:00 h on day 2 (ad libitum feeding day), thus fasting for 36 h. On the 'maintenance' protocol, subjects received a maintenance diet throughout day 1. Throughout day 2 they had ad libitum access to a range of familiar foods, which were the same for both treatments. Body weight, blood glucose and respiratory quotient were used as compliance checks. Hunger was monitored on day's -1, 1 and 2 for the fast treatment only.


RESULTS
On day 2, average energy intake was 10.2 vs 12.2 MJ/day (s.e.d. 1.0) on the post-maintenance and post-fast periods, respectively (P=0.049). Subjects altered feeding behaviour, in response to the fast, only at breakfast time, selecting a higher-fat meal (P<0.005). Compared to day -1, motivation to eat was elevated during the fast (P<0.05). This continued until breakfast was consumed during the re-feeding period (day 2), when values then returned to baseline.


CONCLUSIONS
These data suggest that a 36 h fast, which generated a negative energy balance of approximately 12 MJ, did not induce a powerful, unconditioned stimulus to compensate on the subsequent day.
Johnstone
A M
AM
Rowett Research Institute, Aberdeen, UK. amj@rowett.ac.uk
Faber
P
P
Gibney
E R
ER
Elia
M
M
Horgan
G
G
Golden
B E
BE
Stubbs
R J
RJ
D000328:Adult; D002149:Energy Intake; D005215:Fasting / Q000502:physiology* / Q000523:psychology; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D006815:Hunger / Q000502:physiology; D006963:Hyperphagia / Q000503:physiopathology; D008297:Male; D009752:Nutritional Status