The "results" section of this abstract is awesome. READ IT.

Intermittent fasting for three months decreases pancreatic islet mass and increases insulin resistance in Wistar rats (Bonassa et al., 2018)

Introduction: It is known that fasting causes several physiological changes in the endocrine pancreas, such as insulin secretion, pancreatic islet metabolism and beta cells redox state. However, there is still no consensus about the effects of intermittent fasting (IF), a fad diet widespread by the media and adopted by individuals seeking rapid weight loss. In the present study, we sought to study the effects of the IF diet for three months in an animal model.

Methods: Thirty-day-old female Wistar rats were submitted to IF for three months. During this time body weight and food intake were recorded. After the treatment the animals were killed, and pancreatic islets, perigonadal white adipose tissue, extensor digitorum longus muscle tissue and liver were collected for different analyses.

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Results: IF decreased body weight and food intake. The stomach was greatly increased in size. There was an increase in adipose tissue and a decrease in muscle tissue. IF caused elevation of plasmatic insulin levels, both baseline and after glucose administration. In vitro, IF pancreatic islets had increased insulin secretion, glucose metabolism and net reactive oxygen species production, while decreased their mass. In addition, impairment in AKT phosphorylation was observed in peripheral tissues indicating insulin resistance.

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Discussion: Previous studies showed an increase in orexigenic neurotransmitters production in IF, inducing hunger and hyperphagia in the ad libitum feeding days. Our experiments demonstrate that, despite the weight loss, IF treatment induces undesirable effects on tissue homeostasis. Therefore, the hyperinsulinemia registered in vivo and in vitro, associated with the impairment of glucose tolerance and the decrease in AKT phosphorylation, make clear the occurrence of peripheral insulin resistance. The increased metabolism of pancreatic islets dispersed cells, after IF treatment, indorses the higher insulin secretion. Furthermore, the decrease in the pancreatic islet mass indicates that three months of IF treatment cause severe impairment in glucose homeostasis. In conclusion, intermittent fasting diet may not be healthy to be adopted by individuals seeking rapid weight loss.