Table 4.

Studies on the efficacy of KD in COVID-19 in humans.

	Study Design	Participants (n)/Age (year)	Evaluation	Intervention	Duration	Results	Bibliography
1	Retrospective study in hospitalized patients with COVID-19	EKD n = 34 vs. ESD n = 68	30-day mortality, admission to the intensive care unit; effect of ECD on biological and inflammatory parameters, especially IL-6	ESD 1800–2100 kcal, C: 42–50%, P: 16–20%, F: 26–30%; EKD 1800–2100 kcal, C <30 g, 5–6%, P: 17–18%, and polyunsaturated/unsaturated/saturated fat ratio 3:2:1	follow the diet for a mini-mum of 7 days	-statistically significantly higher survival rates -lower need for intensive care unit hospitalization -reduction in IL-6 between days 0 and 7	Succar et al. (2021) [14]
2	Case report—COVID-19- positive woman, hospitalized for bilateral pneumonia, with sarcopenic obesity, hypertension, hyperinsulinemia, hypercholesterolemia, and hypertriglyceridemia	n = 1, age 55	Anthropometric parameters and body composition, muscle mass and strength, time required to rise from a sitting position without the use of hands, blood pressure, insulin and fasting blood glucose levels, creatinine, triglycerides, LDL cholesterol, HDL cholesterol, vitamin D, and HOMA index	VLCKD (800 kcal/day, C: 28 g (14.6%), F: 35 g (38.7%), P: 85 g (46.7%), 2–2.5 L water/day + interval training 2 times a week 30–35 min/day via the Zoom platform	6 weeks after COVID-19	-reduction of body weight, BMI, amount of body fat, maintenance of lean mass, -improved muscle strength and physical performance -reduction in blood pressure, insulin, glycemia and HOMA, TG, LDL, and creatinine levels -increase in HDL	Camajani et al. [179]
3	A real-world, retrospective exploratory analysis in outpatients with type 2 diabetes, obesity, and positive COVID-19	n = 339, 54.9 ± 8.7 age	hemoglobin A1c, blood glucose, ketone bodies, body weight and body mass index, and assessment of the need for hospitalization	KD—C: <50 g, ~5–10%, P: 1.5 g/kg reference body weight, ~15–20%, F: to satiety ~70–75%	before and during treat-ment	greater weight loss was significantly associated with a lower likelihood of hospitalization	Volk et al. [180]

KD—ketogenic diet, ESD—eucaloric standard diet, EKD—eucaloric ketogenic diet, VLCKD—very low-energy ketogenic diet, P—protein, F—fat, C—carbohydrates, BMI—body mass index, TG—triglycerides, HOMA index—insulin resistance index, hemoglobin A1c—glycated hemoglobin.