While the exact mechanisms are Why do people who eat less live longer? complex and not fully understood, several key factors contribute to this phenomenon:

1. Reduced Metabolic Rate: Calorie restriction lowers the metabolic rate of the body. When fewer calories are consumed, the body adapts by slowing down various metabolic processes. This reduced metabolic rate is believed to reduce the wear and tear on cells and tissues over time.

1. Decreased Oxidative Stress: Calorie restriction can reduce the production of free radicals and oxidative stress. Free radicals are molecules that can cause cellular damage and contribute to the aging process. By consuming fewer calories, the body generates fewer free radicals, potentially leading to healthier cells and tissues.

1. Enhanced Cellular Repair: Calorie restriction may stimulate processes like autophagy, which is responsible for clearing out damaged cellular components. This enhanced cellular repair and maintenance help preserve cell integrity and functionality, contributing to longevity.

1. Improved Insulin Sensitivity: Calorie restriction can improve insulin sensitivity and blood sugar regulation. Enhanced insulin sensitivity is associated with a lower risk of age-related diseases like type 2 diabetes and cardiovascular conditions.

1. Reduced Inflammation: Chronic inflammation is a common factor in many age-related diseases. Calorie restriction can lower the production of inflammatory molecules, resulting in a less inflammatory environment within the body.

1. Altered Gene Expression: Calorie restriction may influence gene expression patterns associated with longevity and aging. It can activate genes that promote longevity while inhibiting those associated with aging-related diseases.

1. Slower Age-Related Changes: Studies in animals have shown that calorie restriction can slow down age-related changes in the body, such as muscle loss, bone density reduction, and cognitive decline.

1. Impact on Hormones: Calorie restriction can affect hormone levels, including growth hormone and insulin-like growth factor-1 (IGF-1), which are linked to aging. Lower levels of these hormones are associated with increased longevity.

It's important to note that while the effects of calorie restriction on lifespan have been demonstrated in various animal models, the translation to humans is complex and not fully established. Extreme calorie restriction without proper nutrition can have adverse effects on health and is not recommended. Instead, a balanced and nutritious diet, regular physical activity, stress management, and other lifestyle factors play essential roles in promoting healthy aging.

In summary, while the connection between calorie restriction and increased lifespan is a subject of ongoing research, it is part of a broader understanding of the complex factors influencing aging and longevity.