Trending Clinical Topic: Intermittent Fasting

Ryan Syrek


March 03, 2023

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The potential of intermittent fasting as an intervention has sparked much recent research. New studies have examined a potential role in nonalcoholic fatty liver disease (NAFLD), type 2 diabetes, and gastroesophageal reflux disease (GERD). However, some findings suggest that the increasingly popular practice may also have a dangerous downside. When it comes to intermittent fasting and NAFLD, the news appears to be quite positive (see Infographic).

In the study, 80 patients with NAFLD were randomized to 3 months of following one of four lifestyle strategies: alternate-day fasting, aerobic exercise, both, or neither. Participants were aged 23-65 years (mean, 44 years), and 81% were women. Half were Hispanic, 30% were Black, 11% were White, and 9% were Asian. They had a mean weight of 218 lb (99 kg) and a mean BMI of 36. The primary outcome was change in intrahepatic triglyceride (IHTG) content from baseline. IHTG content was reduced by a significantly greater amount in the combination intervention group (-5.48%) than in the exercise alone group (-1.30%; P = .02) or the control group (-0.17%; P < .01). It was also greater than in the fasting-only group, although this was not significant (-2.25%; P = .05).

A separate study out of China found that intermittent fasting has the potential to induce remission in patients with type 2 diabetes. The small randomized controlled trial found that 47% of the 36 patients in the fasting group achieved remission (mean A1c, 5.66%) after 3 months of the intervention plus 3 months of follow-up, compared with only 2.8% of the 36 patients in the control group. What's more, 65% of the patients in the intermittent fasting group who achieved remission had had diabetes for longer than 6 years. The strategy consisted of six cycles over 3 months of 5 fasting days followed by 10 ad libitum days, with 3 months of follow-up (no fasting days). At 12 months, 44% of patients in the fasting group had sustained diabetes remission (mean A1c, 6.33%).

Intermittent fasting may also reduce acid exposure time and improve symptoms for individuals with GERD. A small US study of 25 participants with suspected GERD symptoms underwent 96-hour pH monitoring. The mean age was 43.5 years, and 52% were women. Just under half (44%) were White, and the mean BMI was 25.8. They were asked to follow their normal diet for the first 48 hours, followed by a 16-hour fast and then an 8-hour eating window. Only 36% of participants were fully adherent to the regimen; 84% were partially compliant and followed the regimen for at least 1 of the 2 fasting days. Researchers concluded that adhering to the 16:8 regimen reduced mean acid exposure time by 0.64%. On fasting days, the mean acid exposure time was 3.5% compared with 4.3% on the baseline diet. The regimen was also associated with a reduction in GERD symptom scores. After day 4, scores were at 9.9 compared with 14.3 after day 2. Heartburn symptoms scores were reduced by 2.6, and regurgitation scores were reduced by 1.8. When researchers compared participants who were fully compliant with intermittent fasting with those who were only partially compliant, GERD symptoms still improved, with a reduction in scores of 3.2.

As positive as these findings are, the practice of intermittent fasting may have unintended consequences. New findings out of Canada suggest that this dietary change may be linked to eating disorders, including overeating, binge eating, vomiting, laxative use, and compulsive exercise. Researchers analyzed data on 2700 adolescents and young adults aged 16-30 years. The sample included women, men, and transgender or gender-nonconforming (TGNC) individuals. In total, 47% of women (n = 1470), 38% of men (n = 1060), and 52% of TGNC individuals (n = 225) reported engaging in intermittent fasting during the past year. For women, following this practice within the past 12 months and past 30 days were significantly associated with all eating disorder behaviors, as well as higher overall global scores on the Eating Disorder Examination Questionnaire (EDE-Q). For men, fasting in the past 12 months was significantly associated with compulsive exercise and higher overall EDE-Q global scores. For TGNC participants, fasting was positively associated with higher EDE-Q global scores.

From the possibility of helping patients with NAFLD, type 2 diabetes, and GERD to the need for further investigations into long-term implications of the dietary practice, various significant findings about intermittent fasting resulted in its becoming the week's top trending clinical topic.

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