Once the preserve of clinics treating those with morbid obesity, the ketogenic diet is increasingly being spruiked by celebrities with claims it can cure ailments ranging from infertility to insulin sensitivity.

It’s a high-fat, ultra-low-carb diet that comes in various forms, including the standard keto (typically 75% fat, 20% protein and 5% carbohydrate), cyclical keto (combining it with 5-2 intermittent fasting) and targeted keto (combining it with high-intensity exercise).