May 11, 2017
Tick Tock: Time Restricted Feeding
and the Metabolic Circadian Clock

The Salk Institute published a study in May of 2015, subsequently providing an intriguing new aspect to consider amid the world’s obesity and metabolic syndrome pandemic. The study showed mice limited to eating during an 8-hour period (called “time-restricted feeding” or TRF) to be healthier than mice eating freely throughout the day. After 100 days, the mice who ate frequently gained weight, developed high cholesterol and high blood glucose, showed evidence of liver damage and reduced motor control. The mice who ate in TRF fashion weighed 28% less, showed reduced levels of low-grade inflammation and showed no adverse health effects, despite consuming the same amount and type of food.

Lifestyle modifications such as a nutrient-dense diet and daily physical activity are first-line interventions in the treatment of metabolic syndrome. Much of the research to date has focused on nutrition optimization, as well as small, frequent meals throughout the day for blood sugar stabilization. However, the Salk study suggests that spreading food intake throughout the day may disturb metabolic pathways governed by the circadian clock, just as artificial lighting been shown to disrupt sleep-wake cycles.

Human studies have shown similar outcomes to Salk’s 2015 study. The University of California San Diego studied over 2,000 overweight women to find that TRF (a modified version of intermittent fasting) had positive effects on both blood sugar levels and immune markers. The data revealed each 3-hour increase in nighttime fasting was associated with a 4% decrease in postprandial glucose levels, regardless of how much women ate. Moreover, there was also a reduction in breast cancer risk.

Labrix’ salivary hormone test panels can reveal early disruptions in the metabolic process. Elevated androgens (testosterone and/or DHEA) in women are often associated with evolving insulin resistance and can serve as a "red flag" for providers that the body may be struggling to keep blood sugar balanced prior to any overt changes in the bloodwork.

Elevated insulin levels in the blood results in elevated androgen levels because it leads to:

  • Decreased sex hormone binding globulin production in the liver (resulting in higher bioavailable androgen levels)
  • Direct increased ovarian production of androgen
  • Indirect increase in ovarian production of androgen by disordered release of FSH & LH
  • Binding of receptors in the adrenal cortex (zona reticularis), stimulating androgen production
  • Inhibition of hepatic production of insulin-like growth factor binding protein-1


Just as the HPA axis and melatonin levels respond to circadian rhythms, it seems that the metabolic system also responds to this same circadian clock. Consider utilizing Labrix’ hormone testing to elucidate disruptions in the metabolic system. In women, catching early elevations in androgens through salivary testing allows practitioners to potentially implement treatment protocols before more advanced metabolic disruptions are established. Large scale clinical trials are needed to further confirm the potential of TRF to improve metabolic markers, including insulin sensitivity and blood sugar control. However, TRF may prove to create a significant impact on the current metabolic syndrome pandemic.

  • Chaix A, Zarrinpar A, Miu P, Panda S. Time-restricted feeding is a preventative and therapeutic intervention against diverse nutritional challenges. Cell Metab. 2014;20(6):991-1005.
  • Hatori M, Vollmers C, Zarrinpar A, et al. Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet. Cell Metab. 2012;15(6):848-60.
  • Heilbronn LK, Smith SR, Martin CK, Anton SD, Ravussin E. Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. Am J Clin Nutr. 2005;81(1):69-73.
  • Livingstone C, Collison M. Sex steroids and insulin resistance. Clin Sci (Lond). 2002; 102: 151-66.
  • Marinac CR, Natarajan L, Sears DD, et al. Prolonged Nightly Fasting and Breast Cancer Risk: Findings from NHANES (2009-2010). Cancer Epidemiol Biomarkers Prev. 2015;24(5):783-9.
  • Marinac CR, Nelson SH, Breen CI, et al. Prolonged Nightly Fasting and Breast Cancer Prognosis. JAMA Oncol. 2016;
  • Salgin B, Marcovecchio ML, Humphreys SM, et al. Effects of prolonged fasting and sustained lipolysis on insulin secretion and insulin sensitivity in normal subjects. Am J Physiol Endocrinol Metab. 2009;296(3):E454-61.
  • Speroff L. Clinical Gynecologic Endocrinology and Infertility. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.
  • Wegman MP, Guo MH, Bennion DM, et al. Practicality of intermittent fasting in humans and its effect on oxidative stress and genes related to aging and metabolism. Rejuvenation Res. 2015;18(2):162-72.

All information given about health conditions, treatment, products, and dosages are for educational purposes only and do not constitute medical advice.


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