Clinical Trial Summary
Dietary fibers are generally not degraded by the endogenous digestive enzymes, but rather by
the complex ensemble of microorganisms that reside in the human gut [1]. This ensemble,
collectively known as the human gut microbiome, plays a key role in breaking down,
fermenting, and ultimately converting such dietary fibers into a variety of beneficial
metabolites, including most notably, short chain fatty acids (SCFA). These end products of
fibers' fermentation affect host metabolism, immunity, and physiology, and have been
implicated in multiple diseases including obesity, metabolic syndrome, diabetes, and
cardiovascular diseases.
Intermediate fasting, and in particular circadian intermediate fasting (i.e. 16 hours of
fasting followed by 8 hours of allowed eating), has been shown to have positive associations
with multiple health conditions as obesity, diabetes mellitus, cardiovascular disease,
cancers, and neurologic disorders In this study, we will try to answer open questions
utilizing the long fasting period during the day to investigate the isolated effect of
dietary fiber consumption, uncovering the degradation effect, but not the bulking effect, on
the microbiome and the host physiology, and in particular its glucose response.
During the 22 days of the study, participants will wear a continuous glucose monitor, fill a
daily food diary, and collect stool and oral samples which will be used for microbiota
profiling. Participants will be asked to carry out an intermediate fasting regime, which will
include: 16 straight hours of fasting followed by 8 hours which the participants will be
allowed to eat. Drinking water is allowed throughout the fasting hours.
The groups will consume 4, 12, 20 grams of the dietary fiber per day, according to the group
they were assigned to, while not exceeding the total fiber consumption of 50 grams per day,
which is considered a high-fiber diet.
