Long-term (5-year) effects of a reduced-fat diet intervention in individuals with glucose intolerance.
OBJECTIVE
To determine whether reducing dietary fat would reduce body weight and improve long-term glycemia in people with glucose intolerance.


METHODS
A 5-year Follow-up of a 1-year randomized controlled trial of a reduced-fat ad libitum diet versus a usual diet. Participants with glucose intolerance (2-h blood glucose 7.0-11.0 mmol/l) were recruited from a Workforce Diabetes Survey. The group that was randomized to a reduced-fat diet participated in monthly small-group education sessions on reduced-fat eating for 1 year. Body weight and glucose tolerance were measured in 136 participants at baseline 6 months, and 1 year (end of intervention), with follow-up at 2 years (n = l04), 3 years (n = 99), and 5 years (n = 103).


RESULTS
Compared with the control group, weight decreased in the reduced-fat-diet group (P < 0.0001); the greatest difference was noted at 1 year (-3.3 kg), diminished at subsequent follow-up (-3.2 kg at 2 years and -1.6 kg at 3 years), and was no longer present by 5 years (1.1 kg). Glucose tolerance also improved in patients on the reduced-fat diet; a lower proportion had type 2 diabetes or impaired glucose tolerance at 1 year (47 vs. 67%, P < 0.05), but in subsequent years, there were no differences between groups. However, the more compliant 50% of the intervention group maintained lower fasting and 2-h glucose at 5 years (P = 0.041 and P = 0.026 respectively) compared with control subjects.


CONCLUSIONS
The natural history for people at high risk of developing type 2 diabetes is weight gain and deterioration in glucose tolerance. This process may be ameliorated through adherence to a reduced fat intake
Swinburn
B A
BA
Department of Community Health, University of Auckland, New Zealand. swinburn@deakin.edu.au
Metcalf
P A
PA
Ley
S J
SJ
D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001835:Body Weight; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000517:prevention & control*; D018752:Diet, Fat-Restricted; D002149:Energy Intake; D005006:Ethnicity; D005215:Fasting; D005260:Female; D005500:Follow-Up Studies; D018149:Glucose Intolerance / Q000097:blood / Q000178:diet therapy* / Q000534:rehabilitation*; D005951:Glucose Tolerance Test; D006306:Health Surveys; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D010353:Patient Education as Topic; D013997:Time Factors
D001786:Blood Glucose