EndocrinologyDec 15, 2015

Intermittent fasting reduces fat while keeping muscle and increases brain signals that control hunger in obese male mice

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 31, 2026

Abstract

IMF protocols resulted in 13% to 18% lower body weights in obese mice compared to continuous high-fat diet feeding.

Body fat decreased by approximately 40%-52% across all diet interventions.
Lean mass increased by about 12%-13% in the IMF-LFD group compared to the other groups.
Oral glucose tolerance improved, with a reduction of about 50% in the area under the curve for the IMF-HFD group.
Insulin tolerance was lower in all diet interventions, reduced by 22%-42%.
Norepinephrine content in the hypothalamus was higher by 55%-60% in IMF groups compared to ad libitum-fed groups.
Gene expression of neuropeptide Y in the arcuate nucleus increased by 65%-75% in IMF groups.

Simplified

Clinical studies indicate alternate-day, intermittent fasting (IMF) protocols result in meaningful weight loss in obese individuals. To further understand the mechanisms sustaining weight loss by IMF, we investigated the metabolic and neural alterations of IMF in obese mice. Male C57/BL6 mice were fed a high-fat diet (HFD; 45% fat) ad libitum for 8 weeks to promote an obese phenotype. Mice were divided into four groups and either maintained on ad libitum HFD, received alternate-day access to HFD (IMF-HFD), and switched to ad libitum low-fat diet (LFD; 10% fat) or received IMF of LFD (IMF-LFD). After 4 weeks, IMF-HFD (∼13%) and IMF-LFD (∼18%) had significantly lower body weights than the HFD. Body fat was also lower (∼40%-52%) in all diet interventions. Lean mass was increased in the IMF-LFD (∼12%-13%) compared with the HFD and IMF-HFD groups. Oral glucose tolerance area under the curve was lower in the IMF-HFD (∼50%), whereas the insulin tolerance area under the curve was reduced in all diet interventions (∼22%-42%). HPLC measurements of hypothalamic tissue homogenates indicated higher (∼55%-60%) norepinephrine (NE) content in the anterior regions of the medial hypothalamus of IMF compared with the ad libitum-fed groups, whereas NE content was higher (∼19%-32%) in posterior regions in the IMF-LFD group only. Relative gene expression of Npy in the arcuate nucleus was increased (∼65%-75%) in IMF groups. Our novel findings indicate that intermittent fasting produces alterations in hypothalamic NE and neuropeptide Y, suggesting the counterregulatory processes of short-term weight loss are associated with an IMF dietary strategy.

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Intermittent fasting reduces fat while keeping muscle and increases brain signals that control hunger in obese male mice

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