Low-Carbohydrate and Ketogenic Diets

Low-carbohydrate diets reduce carbohydrate (often below ~100–150 g/day), replacing it with protein and fat. The ketogenic (keto) diet is the extreme version: carbohydrate is cut to roughly 20–50 g/day (~5–10% of calories), fat is high (~70%+), forcing the body to produce ketone bodies from fat as an alternative fuel — a state called nutritional ketosis.

Pros: Often produces effective short-term weight loss (partly rapid initial loss of glycogen-bound water — see glycogen), strong appetite suppression for many, and meaningful blood-glucose and triglyceride improvements in type 2 diabetes and metabolic syndrome. Some people find the simplicity and satiety easy to follow.

Cons / considerations: When calories and protein are matched, low-carb diets show no consistent fat-loss advantage over higher-carb diets — the benefit is largely from eating fewer total calories. The "keto flu" (fatigue, headache, irritability) is common in the first week. Carbohydrate restriction can impair high-intensity and glycolytic exercise and is generally counterproductive for endurance and power performance that rely on glycogen (see endurance-fueling). It can be socially restrictive and may raise LDL in some individuals; fiber and certain micronutrients need attention. As always, adherence decides long-term results (see diet-adherence-principle).

• Low-carb: carbs often <100–150 g/day; keto: ~20–50 g/day (~5–10% cal), high fat, ketosis.
• Effective short-term weight loss; initial drop partly glycogen-water.
• With calories/protein matched, no inherent fat-loss edge over higher-carb.
• Helps glycemic control in T2D/metabolic syndrome.
• Can impair high-intensity/endurance performance; "keto flu" early on.

• carbohydrates — the macronutrient being restricted.
• glycogen — water loss explains rapid early scale change.
• diet-adherence-principle — adherence drives outcomes.
• endurance-fueling — why low-carb hurts glycogen-dependent performance.