The Hunger Hormones: Ghrelin and Leptin During Fasting
Understanding ghrelin and leptin—the two primary hunger hormones—is crucial for anyone practising intermittent fasting or a ketogenic diet. These hormones regulate appetite, energy balance, and fat storage. Research suggests ketogenic diets may influence their behaviour during fasting periods differently than other dietary approaches.
How Ghrelin Works
Ghrelin, produced in the stomach, signals hunger to the brain. Levels typically rise before meals and fall after eating. During prolonged fasting, ghrelin secretion follows a wave-like pattern rather than increasing linearly. A 2013 study found that after weight loss, ghrelin levels remained elevated in those on low-fat diets but stabilised in low-carbohydrate groups (Sumithran et al., 2013).
Leptin’s Role in Satiety
Leptin, secreted by fat cells, communicates energy sufficiency to the hypothalamus. Obesity often leads to leptin resistance, where the brain ignores these signals. Ketogenic diets appear to improve leptin sensitivity, potentially due to reduced inflammation and improved metabolic markers (Volek et al., 2008).
What This Means in Practice
At Tesco, a 500g pack of free-range eggs costs £2.20—an excellent source of protein and fat to support hormonal balance during fasting. The UK’s variable weather means hydration needs change seasonally; adding electrolytes becomes particularly important during summer fasts. Those managing intermittent fasting schedules often report easier adaptation when combining keto with fasting.
Frequently Asked Questions
1. Does fasting increase ghrelin long-term? Short-term fasting causes ghrelin fluctuations, but studies suggest levels adapt over weeks. The ketogenic diet may help stabilise this response compared to high-carb diets (40-60 words).
2. Can leptin resistance be reversed? Research indicates that reducing insulin resistance through low-carb diets may improve leptin sensitivity. This process typically takes several months of consistent dietary change (50-70 words).
3. How does exercise affect these hormones? Moderate exercise appears to temporarily suppress ghrelin while enhancing leptin sensitivity. However, intense endurance exercise without adequate nutrition may have the opposite effect (60-80 words).
The Bottom Line
Ghrelin and leptin represent complementary systems regulating hunger and satiety during fasting. Emerging evidence suggests ketogenic diets may positively influence both hormones compared to other dietary approaches. For those tracking macros while fasting, keto electrolyte supplementation becomes crucial. If you’d rather not do the macro maths yourself, the Keto Dieting app does it for you on Google Play and the App Store.
References
- Sumithran P, Prendergast LA, Delbridge E, et al. (2013). Ketosis and appetite-mediating nutrients and hormones after weight loss. European Journal of Clinical Nutrition. https://doi.org/10.1038/ejcn.2013.90
- Volek JS, Phinney SD, Forsythe CE, et al. (2008). Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low fat diet. Lipids. https://doi.org/10.1007/s11745-008-3274-2
