Does low carbohydrate intake lead to increased cortisol production?

Low Carbohydrate Diets and Cortisol Production

Low carbohydrate diets, particularly in the short term (less than 3 weeks), do increase cortisol production, which may have negative implications for stress levels and metabolic health. 1

Relationship Between Carbohydrate Restriction and Cortisol

Short-term Effects

• Low-carbohydrate diets moderately increase resting cortisol levels during the first 3 weeks of implementation 1
• The cortisol response is more pronounced during the initial adaptation period to carbohydrate restriction
• Exercise during this adaptation period results in significantly higher post-exercise cortisol levels compared to higher carbohydrate diets 1, 2

Long-term Effects

• After approximately 3 weeks, resting cortisol levels appear to return to baseline on low-carbohydrate diets 1
• However, post-exercise cortisol remains elevated even after adaptation to a low-carbohydrate diet 1, 2
• This suggests that while the body adapts to some degree, metabolic stress during physical activity remains higher on carbohydrate-restricted diets

Factors Affecting Cortisol Response

Degree of Carbohydrate Restriction

• Very low-carbohydrate diets (<26% of total energy) produce more significant hormonal effects than moderate carbohydrate restriction 3
• Fasting shows a very strong effect in increasing serum cortisol, while less severe caloric restriction has minimal impact 4

Protein Intake

• High-protein (≥35% of calories), low-carbohydrate diets may have additional hormonal effects, including decreased testosterone levels 1
• This combination could potentially compound stress-related effects

Duration of Diet

• Meta-regression analysis shows a negative association between serum cortisol levels and the duration of caloric restriction 4
• This indicates the cortisol response may be highest during the initial adaptation period

Clinical Implications

Metabolic Considerations

• Elevated cortisol can promote:
  • Increased blood glucose levels
  • Insulin resistance
  • Muscle protein breakdown
  • Potential weight gain, particularly abdominal fat 5

Exercise Performance

• Low-carbohydrate diets result in reduced workload capacity and higher perceived exertion during exercise 2
• This effect persists even after two weeks of adaptation 2

Psychological Effects

• Caloric restriction increases perceived stress 5
• This combination of physiological and psychological stress may contribute to difficulty adhering to restrictive diets

Recommendations for Practice

• For most individuals, extremely low carbohydrate intake (<26% of calories) should be limited to short durations (up to 3-4 months) if implemented at all 3
• Focus on high-quality, minimally processed carbohydrate sources rather than extreme restriction 3, 6
• Monitor for signs of increased stress, fatigue, or exercise intolerance when following low-carbohydrate diets
• Consider a more moderate carbohydrate approach (30-45% of calories) from high-quality sources for long-term health 3, 6
• Individuals with existing stress-related conditions should be particularly cautious with very low carbohydrate approaches

Special Considerations

• Very-low-carbohydrate diets require medical supervision and are not recommended for:
  • Pregnant or lactating women
  • Children
  • People with kidney disease
  • Those with or at risk for disordered eating 3
  • People taking SGLT2 inhibitors (risk of ketoacidosis) 3

The evidence clearly shows that while low-carbohydrate diets may have benefits for certain conditions, they do induce a stress response as measured by cortisol production, particularly in the initial adaptation phase and during exercise.