Research perspective · 11 September 2026
Can under-fuelling disrupt sleep?
Human evidence links some forms of energy restriction to disturbed sleep, but the response depends on the exposure and population.
What the human studies show
A calorie deficit can affect sleep, but a uniform response is not established. In a small study of 17 women without obesity, five days with a 55% reduction in energy availability was followed by greater actigraphic sleep fragmentation. The non-randomised diet sequence and small completing sample limit causal confidence. Associations with circulating orexin do not demonstrate that brain orexin caused the changes. [1]
In 42 adolescent male rugby players, lower estimated energy availability was associated with poorer sleep measured by overnight polysomnography. This was observational: training, stress and other factors could contribute. Exploratory energy-availability breakpoints were not validated diagnostic thresholds. [2]
Restriction does not always worsen sleep
CALERIE 2 found no overall deterioration in self-reported sleep during two years of moderate calorie restriction in healthy adults without obesity. A sleep-duration subscale favoured restriction at 12 months. In another experiment involving 12 men, two days at 10% of estimated energy requirements increased a deep-sleep measure without significantly changing total sleep duration, efficiency or awakenings. Differences in severity, duration, sex and measurement matter. [3,4]
Does the brain run out of glucose overnight?
Fasting humans produce glucose through hepatic glycogen breakdown and gluconeogenesis. Eating less therefore does not automatically mean blood glucose becomes dangerously low during sleep. [6]
Insulin-induced nocturnal hypoglycaemia at about 2.2 mmol/L caused awakening in 10 of 16 healthy participants, compared with one of 16 participants with type 1 diabetes. This demonstrates a response to experimentally induced hypoglycaemia; it does not show that ordinary dieting causes night waking through the same mechanism. Hunger on waking is not a glucose measurement. [5]
A useful EPK research question
Does improving energy availability improve objectively measured sleep in people with persistent under-fuelling, independently of training load, psychological stress and weight change? Sleep is a candidate outcome for EPK research, not a diagnostic test of an EPK state. Intake per kilogram of body weight, energy availability per kilogram of fat-free mass, resting expenditure and blood glucose must be measured and reported separately. These studies do not validate a universal 25 kcal/kg/day minimum.
Research and guidance
Explore more studies in the research library.
- Kim, Shekhar et al. (2025). Caloric Restriction, the Menstrual Cycle, and Sleep in Women Without Obesity.
- Saidi et al. (2024). Association between Low Energy Availability (LEA) and Impaired Sleep Quality in Young Rugby Players.
- Martin et al. (2016). Effect of Calorie Restriction on Mood, Quality of Life, Sleep, and Sexual Function in Healthy Nonobese Adults: The CALERIE 2 Randomized Clinical Trial.
- Collet et al. (2016). The Sleep/Wake Cycle is Directly Modulated by Changes in Energy Balance.
- Schultes et al. (2007). Defective Awakening Response to Nocturnal Hypoglycemia in Patients with Type 1 Diabetes Mellitus.
- Rothman et al. (1991). Quantitation of hepatic glycogenolysis and gluconeogenesis in fasting humans with 13C NMR.
Related working papers
Read the relevant PDFs: EPK–001 to 007 are the revised version 1.2 papers; EPK–008 to 010 are version 1.0 supplements. Earlier PDFs and DOI records remain on the paper archive.