Greek Orthodox fasting alters body chemistry, study finds

A study of Orthodox Christians in Greece has shed new light on the health benefits of plant-based diets. Researchers observed that abstaining from meat, fish, dairy, and eggs for extended periods, as part of religious practice, significantly alters body chemistry.

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This dietary regimen represents a real dietary pattern that is strongly motivated by religious beliefs and is usually part of the culture of the family into which people who practice it are born.

The study focused on 200 healthy individuals who followed a vegan diet for 180-200 days each year, a practice common among Orthodox Christians during religious fasting periods. These fasts include Wednesdays and Fridays weekly, and four longer periods throughout the year, such as the 40 days before Christmas and 48 days before Easter.

Researchers noted that this dietary regimen, motivated by religious beliefs and cultural traditions, leads to a reduction in animal fat intake. It also affects protein intake, as participants abstain from most animal protein sources without a decrease in overall energy consumption. This consistent pattern makes the practice an almost ideal natural experiment for studying dietary impacts on gene activity.

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During the restriction of animal products, in addition to a marked reduction in the intake of animal fats, people who occasionally practice restriction reduce their protein intake (as a proportion of total energy intake).

Comparing participants to a control group of 211 individuals who did not observe these dietary restrictions, scientists found notable changes in body chemistry, especially in gene expression. Previous research indicated that this fasting leads to metabolic reprogramming with health benefits, including altered levels of key immunometabolic proteins like FGF21.

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The consistency of this dietary pattern and the predictability of the transition between omnivorous and animal product restriction diets make this study comparable to a dietary intervention study.

The new study further discovered that participants with a specific gene variant regulating FGF21 levels, who also practiced the meat-free fast, showed physiological signs potentially linked to "beiging" of adipose tissue. This process, where white fat cells start behaving more like heat-generating brown fat cells, suggests that FGF21 levels induced by fasting might play a role in this metabolic shift. While these findings require cautious interpretation, they offer intriguing insights into how dietary changes can influence fat metabolism.

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Although these findings should be interpreted with caution, it is possible that the FGF21 levels induced by fasting are associated with the process of "beiging" of adipose tissue.