What causes initial weight gain when starting a ketogenic (keto) diet?

From the Guidelines

Weight gain when starting a keto diet is often temporary and can be attributed to water retention, hormonal fluctuations, and increased calorie intake from high-fat foods, as noted in recent studies on ketogenic diets 1. When initiating a ketogenic diet, the body undergoes significant changes, including a shift from relying on glucose to ketones for energy production. This transition can lead to initial weight gain due to several factors.

• Water retention is a common issue, as the body adjusts to lower carbohydrate intake and potentially increased salt consumption to maintain electrolyte balance.
• Hormonal fluctuations also play a role as the body adapts to using ketones instead of glucose for energy.
• Additionally, some individuals may consume too many calories on a keto diet by overindulging in high-fat foods like cheese, nuts, and oils, which are calorie-dense despite being keto-friendly.
• Building muscle through exercise while on keto can also register as weight gain on the scale. It's essential to track calorie intake carefully, maintain proper hydration, ensure adequate protein consumption, and be patient with the adaptation process, as this initial weight gain typically resolves within a few weeks as the body becomes fat-adapted, according to the principles of ketogenic diets outlined in recent research 1.
• Monitoring changes in body composition, such as fluid shifts and skeletal muscle mass, can help individuals understand short-term shifts in weight and hydration status, as discussed in the context of bioelectrical impedance analysis for assessing body composition during ketogenic diets 1.
• The utilization of bioelectrical impedance analysis (BIA) is becoming increasingly popular in monitoring changes in body composition parameters of interest in ketogenic diet research, including fluid changes and skeletal muscle mass 1.

From the Research

Weight Gain on the Keto Diet

• There is limited research directly addressing why someone would gain weight when first starting the keto diet, but several studies provide insight into the diet's effects on weight and metabolism 2, 3, 4.
• The ketogenic diet is a very low-carbohydrate, high-fat diet that has been shown to induce effective weight loss and improvement of several parameters of cardiovascular risk in the short and medium term 2, 4.
• However, some studies suggest that the keto diet may not be suitable for everyone, and its effects on weight and metabolism can vary depending on individual factors 3, 5.
• One possible explanation for weight gain on the keto diet is that it can be difficult to adhere to the diet's strict carbohydrate restrictions, leading to overconsumption of calories or poor food choices 6.
• Additionally, the keto diet can cause changes in water weight and electrolyte balance, which may lead to temporary weight gain 3.

Physiological Effects of the Keto Diet

• The keto diet causes the body to enter a state of ketosis, in which it burns fat for fuel instead of carbohydrates 2, 6.
• This metabolic shift can lead to changes in hormone levels, including increases in cortisol and adrenaline, which can affect appetite and metabolism 3.
• The keto diet can also affect gut health and the microbiome, which can influence weight and metabolism 5.
• Some studies suggest that the keto diet may have negative effects on certain health markers, such as LDL cholesterol and triglycerides, which could contribute to weight gain or other health problems 3, 5.

Individual Variability and the Keto Diet

• The keto diet may not be suitable for everyone, and individual results can vary widely 3, 5.
• Factors such as age, sex, body composition, and overall health can influence the effectiveness of the keto diet for weight loss and overall health 2, 4.
• Some people may experience adverse effects or difficulties adhering to the keto diet, which can lead to weight gain or other negative outcomes 6, 5.
• More research is needed to fully understand the effects of the keto diet on weight and metabolism, as well as its potential risks and benefits for different populations 2, 3, 5.