medwireNews: Restricting fast-day eating to the morning has a positive effect on postprandial glucose versus standard calorie restriction among people at increased risk for type 2 diabetes who are trying to lose weight, a study shows.
Reporting the findings in Nature Medicine, the researchers say that while previous studies have shown improved insulin sensitivity with intermittent fasting versus a standard calorie-restricted diet, postprandial responses to a mixed meal are “more highly predictive of type 2 diabetes and cardiovascular disease, and provide more physiological relevance than oral glucose tolerance tests.”
The 85 people randomly assigned to intermittent fasting in this trial had 3 nonconsecutive days on which they consumed 30% of their baseline energy requirements between the hours of 08:00 and 12:00 and fasted for the remaining 20 hours.
Leonie Heilbronn (The University of Adelaide, South Australia) and co-researchers chose this timing because of preclinical evidence that calorie intake during the active rather than rest phase maximizes its benefits.
However, they concede that requiring people to skip dinner several days each week could result in low persistence with the diet, noting that only 46% of the fasting-diet group in this trial were keen to continue a 3 days/week regimen after month 6, with most of the remainder preferring to reduce to 2 days. This compared with 97% of the participants who continued to follow the calorie-restricted diet.
The team calls for future studies to assess if an eating window such as 08:00 to 16:00 hours might replicate the benefits seen in this study while being “more sustainable long-term.”
The 83 people allocated to standard calorie restriction were asked to reduce their daily calorie intake by 30%. Both groups were allowed to use meal replacements to help them achieve their calorie goals. The study participants were an average age of 58 years, 57% were women, and all were at increased risk for type 2 diabetes according to the AUSDRISK score.
The primary outcome was change in postprandial glucose area under the curve (AUC) between baseline and month 6, and this reduced significantly more in the time-restricted intermittent fasting group than the calorie restriction group, at 10.10 versus 3.57 mg/dL per min.
Both diet groups had reductions in postprandial AUC compared with a control group of 41 people who continued with their usual eating habits, and they also had a significant reduction in glycated hemoglobin. In addition, both intervention groups lost significantly more weight than the control group, by approximately 4.5 kg.
Of note, the time-restricted fasting group had significantly lower fasting triglyceride levels than both the calorie-restriction and control groups at month 6.
By month 18, no significant differences in glycemic or cardiovascular risk markers, or in bodyweight, remained between the two intervention groups, or versus the controls, leading the researchers to conclude “that neither regimen was more sustainable when support from the investigators was withdrawn.”
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