Influence of Stress on Calorie-Restricted Diets and Lifespan

Stress may be the main culprit for a declined lifespan despite a healthy lifestyle.

Reviewed by Michelle Quirk

Key points

• Decreasing calorie intake in mammals can increase their lifespan.
• Stress resulting from the suppression of immune responses in aged cells disrupts calorie-restricted diets.
• Lifestyle alterations and psychological strategies may combat the adverse effects of stress on longevity.

For decades, scientists have recognized that calorie restriction can lead to a longer life and better health. However, a recent study published in Nature raises questions about this idea. The research highlights how diet, genetics, and psychological resilience interact to affect lifespan in mice.

Researchers at The Jackson Laboratory studied nearly 1,000 genetically diverse female mice on different diets to test the theory that eating less results in longer life. They found that mice on very low-calorie diets (60 or 80 percent of their normal intake) lived significantly longer than those with no dietary restrictions. Mice on unrestricted diets lived an average of 25 months, while those on intermittent fasting lived about 28 months. Mice consuming 80 percent of their baseline calories averaged 30 months, and those on a 60 percent intake had the longest lifespan at around 34 months.

Interestingly, the longest-lived mice lost the least weight while on calorie-restricted diets. Mice that lost significant weight often had low energy and weaker immune systems, which led to shorter lifespans. This suggests that maintaining body weight during calorie restriction is important for longevity. The researchers also noted that factors like genetic differences, resilience, and immune health might play a role in lifespan and health span.¹

The immune system plays a major role on aging-related conditions and health span.

The immune system is key to aging-related conditions and overall health. One theory of aging suggests that the buildup of old cells in tissues leads to dysfunction and accelerates aging. These aged cells, known as senescent cells, stop dividing and release chemicals that cause inflammation. These chemicals attract immune cells to remove the senescent cells. However, if these cells aren't cleared away, chronic inflammation can occur. This inflammation can spread the aging traits to nearby and distant cells, promoting aging in other tissues.

If the immune system struggles to manage these senescent cells, it can worsen their accumulation and speed up aging. This theory highlights the immune system's central role in either delaying or accelerating age-related conditions, with the aging of immune cells being a major factor in speeding up the aging process. Several factors influence the proper immune response to remove senescent cells including chronological aging, obesity, diabetes, diets, and psychological stress. On the other hand, immunosenescence promotes age-related diseases such as cardiovascular diseases, neurodegenerative illnesses, cancers, and diabetes.²

Stress impairs the immune system's ability to respond effectively.

Chronic psychological stress can disrupt the normal immune response, impairing the body's ability to eliminate pathogens and senescent cells. This disruption occurs through the release of stress hormones, such as cortisol, which can alter the function of immune cells, making them less effective at fighting off potential senescent cells and promoting inflammation that may contribute to aging development. During periods of stress, the body releases hormones like cortisol and adrenaline, which can suppress the immune system by altering the activity of white blood cells, making them less efficient at detecting and destroying abnormal cells, including senescent cells. Additionally, stress can lead to increased regulatory T cells (Tregs), which function as "brakes" on the immune system, preventing it from attacking abnormal cells. The immune system dysfunction ultimately results in prolonged inflammation, which is considered a major factor in age-related diseases, including metabolic disorders and cancer, and subsequently contributes to a decline in lifespan. Moreover, sustained inflammation reduces the effectiveness of calorie-restricted diets and contributes to resistance to weight loss, as well as weight regain after successful weight loss.³

How can we mitigate the negative impact of stress on immune function?

To combat the adverse effects of stress on normal immune response and decrease chronic inflammation, there is a combination of lifestyle changes, psychological strategies, and possibly medical interventions.

1. Mindfulness and Relaxation Techniques

• Meditation: Practices like mindfulness meditation can help reduce stress and improve immune function.
• Deep Breathing Exercises: Techniques such as diaphragmatic breathing can activate the relaxation response.
• Yoga and Tai Chi: These practices combine physical movement with mindfulness, promoting relaxation and reducing stress.

2. Exercise and Increased Physical Activity

Regular exercise has been shown to reduce stress hormones, improve mood, and enhance immune function. Aim for at least 150 minutes of moderate-intensity exercise per week.

3. Healthy Diet

A balanced diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats can support immune health. Foods high in antioxidants, such as berries and nuts, can help combat inflammation. Omega-3 fatty acids, found in fish, flaxseeds, and walnuts, possess anti-inflammatory properties.

4. Adequate Sleep

Prioritize getting 7 to 9 hours of quality sleep per night. Poor sleep can negatively impact immune function and increase stress levels.

5. Limiting Stimulants and Alcohol

Reduce intake of caffeine, nicotine, and alcohol, as these can exacerbate stress and disrupt sleep.

6. Normal Microbiome

Keeping a normal balance of gut microbiota is very important for a healthy immune response. Eating a healthy and balanced diet, and using prebiotic and probiotic supplements if needed and advised by a doctor, can help maintain a healthy gut microbe population and support the immune system.

Genetic, lifestyle, and psychological factors influence both a person's lifespan and health span, the latter referring to the period of healthy aging. It appears that the health of the immune system plays a significant role in determining both lifespan and health span. Therefore, to achieve the best health outcomes from calorie-restricted diets, keeping the health of the immune system is one of the major factors.