How HIIT and intermittent fasting alter metabolism in postmenopausal women

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Mar 28 2025

New research uncovers how pairing intermittent fasting or low-calorie diets with high-intensity interval training can boost metabolism, burn fat, and enhance physical performance in postmenopausal women.

Study: Influence of Intermittent Fasting on Body Composition, Physical Performance, and the Orexinergic System in Postmenopausal Women: A Pilot Study. Image Credit: pics five / Shutterstock.com

A recent study published in Nutrients determines how the combination of high-intensity interval training (HIIT) with either intermittent fasting (IF) or a low-calorie diet (LCD) improves metabolic health among postmenopausal women.

How do nutrition and exercise improve menopause symptoms?

Menopause leads to numerous physiological changes, some of which include increased visceral fat and reduced muscle mass. These changes, most of which can be attributed to reduced estrogen levels, can lead to systemic inflammation, insulin resistance, and an increased risk of metabolic dysfunction.

Various strategies are recommended to postmenopausal women to manage these issues, including a combination of both nutritional and exercise interventions to support metabolic health. IF is a nutritional approach that involves alternating periods of eating with long fasting durations. The 16:8 diet, for example, recommends 16 hours of fasting and an eight- hour eating window during a 24-hour period.

IF also alters the levels of appetite-related hormones like orexin-A (OX-A), which is hypothalamic hormone that maintains energy balance and regulates eating behaviors. Fasting activates orexin neurons, thereby stimulating appetite-increasing hormones like neuropeptide Y (NPY) and agouti-related peptide (AgRP). Both NPY and AgRP exert sympathetic activity that leads to heat production and fat breakdown, which restores energy supplies to cells during fasting-induced stress.

Previous studies have reported that IF supports metabolic flexibility, during which cells throughout the body can transition between using glucose or fat as their primary source of energy. These responses promote the oxidation of fat, improve insulin sensitivity, and reduce inflammation through various biological mechanisms, some of which include increased adenosine monophosphate (AMP)-activated protein kinase (AMPK) activity and autophagy, supporting mitochondrial function, and antioxidant effects.

HIIT synergistically improves these metabolic and appetite-related responses by causing acute metabolic stress, even as it enhances cardiorespiratory fitness. Many of the biological mechanisms implicated in the health benefits of HIIT are shared with IF, with higher OX-A levels associated with the combination of both HIIT and IF than either alone. OX-A stimulates brain reward pathways, which provides motivation for more physical activity while improving metabolic flexibility and promoting fat oxidation.

Study findings

The current study included 30 postmenopausal women with an average age of 57.5 years who were exposed to either the LCD or IF along with HIIT for eight weeks. At baseline, the LCD group had better endurance and flexibility as compared to the IF group. Baseline exercise tolerance and aerobic capacity were higher in the IF group.

Both LCD and IF combined with HIIT improved metabolism, physical performance, and neurohormonal signaling in postmenopausal women. Whereas LCD relied on caloric restriction to reduce fat mass, IF improved metabolic switching and promoted fat burning.

The IF-HIIT group experienced significant improvements in their physical performance parameters, of which included flexibility and maximum oxygen uptake (VO2), at the end of the eight-week study period. Study participants in the IF-HIIT group also exhibited greater mean heart rates and endurance as compared to the LCD-HIIT group.

OX-A levels changed significantly over the intervention period, favoring the IF group. The baseline average OX-A level for the IF group exceeded that of the LCD group.

At eight weeks, OX-A evels tripled in the IF-HIIT group, with an over two-fold increase as compared to LCD-HIIT levels. Nevertheless, LCD was associated with reduced fat mass and improved insulin sensitivity.

Conclusions

The combination of IF and HIIT offers a dual-action strategy, enhancing metabolic flexibility while stimulating the orexinergic system to mitigate the metabolic decline associated with menopause.”

Both IF and LCD provide metabolic benefits, particularly when combined with HIIT in postmenopausal women, which may be due to alterations in the appetite-regulating system. These changes were induced by acute metabolic stress due to HIIT, as well as repeated switching between fat and carbohydrate utilization for energy due to IF.

The study findings suggest that the combination of both IF and HIIT is a promising approach to weight management and metabolic regulation in postmenopausal women. Nevertheless, future research is needed to elucidate how these metabolic and exercise-related shifts occur, as well as the long-term effects of IF and HIIT.