How does under-eating affect metabolism?

Under-eating can significantly impact metabolism and overall health. When you consistently consume fewer calories than your body needs, your metabolism adjusts by slowing down to conserve energy. This adaptation can make it harder to maintain weight loss and may even lead to weight gain over time as your body clings to calories more efficiently.

Key Effects of Under-Eating:

1. Decreased Metabolic Rate: Chronically under-eating reduces your resting metabolic rate since your body tries to preserve energy under perceived scarcity conditions. This is similar to how a car would adjust its mileage if it received less fuel regularly 1 2.
2. Hormonal Imbalances: Chronic calorie restriction can disrupt hormones like thyroid hormones, which are crucial for metabolism. It can also impact cortisol levels, ghrelin, and leptin, affecting hunger and satiety 2 3.

   Understanding the Undereat-Overeat Cycle

   Steph Hnatiuk, RD

   Elisabeth Scott

   Steph explains the unintended consequences of cyclical undereating and overeating, including decreased resting metabolism, diminished exercise motivation, and lower calorie burn during workouts. She also highlights the implications from a hormone perspective and the impact on body composition.

   

   The Running Explained Podcast

   s2/e09 Body Composition & Recomposition for Runners with Steph Hnatiuk, RD (@steph.the.runners.dietitian)

   Explore similar conversationsView full episode summary

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3. Performance and Motivation: Lack of proper nutrition can lead to decreased exercise motivation and performance since the brain and muscles lack sufficient fuel. This often results in a vicious cycle of under-eating and overeating, which further disrupts metabolism and body composition 1 3.
4. Health Consequences: Long-term under-eating can lead to nutrient deficiencies, adversely affecting organs, bones, skin, and overall health. Conditions like osteoporosis are more common among those who habitually under-eat, highlighting the broad impact on physical health 4.

Practical Insights:

• Metabolic Adaptation: Your body adapts to lower calorie intake by becoming more efficient, often leading to challenges in achieving and maintaining weight loss 2 5.
• Importance of Adequate Intake: To avoid these negative effects, it's crucial to ensure you're consuming enough calories and nutrients to support your body's needs, including periods of caloric maintenance or surplus to boost metabolism and muscle mass 2.

Understanding these impacts can help inform healthier dietary practices, emphasizing balanced nutrition over chronic calorie restriction.