Lifespan Vs. Healthspan: Critical Role of Various Dietary Approaches in Healthy Ageing

The global population has grown significantly in the past century, nearly tripling from about 3 billion in 1950 to 8 billion in 2022. Alongside this population surge, life expectancy has increased from 45.51 years in 1950 to 73.16 years in 2023, with projections indicating it may reach 81.88 years by 2100. However, declining fertility rates and longer lifespans have led to an ageing population. While life expectancy is a key measure of a population’s health, its interpretation is complex and influenced by various factors.

The ageing process is highly individualized, and chronological age (CA) alone does not accurately reflect physiological ageing. Researchers are working to find biological indicators to measure ageing better. Although lifespan has increased, healthspan—defined as the period of well-being—has not followed suit, presenting a challenge for societies.

Chronological age refers to the time since a person was born, measured in years, months, and days. It's the most common way people define their age and is a crucial risk factor for chronic diseases, mortality, and bodily impairments, such as hearing loss or memory decline. In contrast, biological age, also known as physiological or functional age, reflects how well or poorly a person’s body has aged on a cellular and tissue level. This age is influenced by factors such as genetics, lifestyle choices, nutrition, and existing health conditions. For example, someone who leads an unhealthy lifestyle—like poor diet, lack of exercise, and smoking—could have a biological age older than their chronological age. While chronological age is fixed, biological age can vary and is calculated using medical assessments and mathematical models to evaluate how well a person’s body functions. Thus, someone might have a chronological age of 28 but a biological age that reflects an older or younger physical condition based on their overall health and lifestyle choices.

The World Health Organization (WHO) defined Healthy Ageing as “the process of developing and maintaining the functional ability that enables wellbeing in older age”.

Functional ability includes a person’s ability to meet their basic needs, learn, grow and make decisions, and their possibility of walking freely and building or maintaining relationships, thus contributing to society's needs. Promoting healthy ageing is crucial, and nutritional interventions have shown promise in improving health outcomes. Furthermore, interventions targeting the ageing process are essential, especially considering the link between ageing, comorbidities, and age-related diseases.

How does diet influence ageing?

Research on ageing has uncovered critical molecular mechanisms that regulate the rate of ageing and lifespan. A primary focus is the mTORC1 (mechanistic target of rapamycin complex 1) pathway, which plays a critical role in cell growth, survival, and autophagy. Reduced mTORC1 signalling has been linked to longer lifespans in various organisms. The mTOR pathway has two complexes, mTORC1 and mTORC2, each affecting different cellular processes. Sustained mTORC1 activation, particularly during senescence, may contribute to age-related decline. The diet also plays a crucial role in ageing.

Caloric restriction (CR), which reduces calorie intake without causing malnutrition, has been shown to extend lifespan and delay ageing in many species. CR works by reducing oxidative stress, inflammation, and cellular ageing. It also regulates nutrient-sensing pathways like TOR, which controls cell growth, metabolism, and autophagy. Intermittent fasting impacts pathways like AMPK and mTOR, improving energy regulation and potentially delaying ageing. Other diets, like the Mediterranean diet, are rich in omega-3 fatty acids and have anti-inflammatory effects that may protect against age-related diseases. The ketogenic diet (KD), by promoting ketone body production and reducing glycolysis, supports insulin sensitivity, glucose regulation, and mitochondrial health. These dietary approaches offer promising ways to promote healthy ageing and extend lifespan.

In this article, we will look at the evidence on the effects of Calorie Restriction (CR), Intermittent Fasting (IF), and Mediterranean Diet (MedDiet) on ageing and health outcomes.

Calorie Restriction

Calorie restriction (CR), which involves reducing calorie intake below daily energy needs while ensuring adequate nutrition, is the only known dietary approach that may slow ageing. Studies from animal and human trials suggest CR can extend lifespan by 1–5 years, improve overall health, and enhance quality of life. CR promotes cellular and metabolic changes that reduce the risk of developing age-related diseases, especially heart-related conditions. However, implementation of CR may require unique considerations for the elderly and other specific populations. In a study by Ravussin and colleagues, 218 non-obese participants aged 21 to 51 were assigned to either a 25% calorie-restricted diet or a regular diet. Over two years, the CR group experienced weight loss, lower levels of inflammation (as indicated by reduced tumour necrosis factor-α), improved cholesterol levels, and changes in metabolism. Although these findings suggest CR benefits cardiometabolic health, its long-term effects on ageing are still unclear. A follow-up study based on data from the CALERIE trial found that CR significantly slowed biological ageing. Using the Klemera–Doubal method (KDM), it was shown that while participants on a regular diet aged 0.71 years annually, those on a calorie-restricted diet only aged 0.11 years per year, demonstrating a notable slowing of the ageing process.

Intermittent Fasting

Intermittent fasting (IF) involves cycles of eating and fasting, with periods ranging from 16 to 48 hours without food, followed by normal eating. IF involves alternating periods of eating and fasting, with no food consumed during fasting times. Popular IF methods include:

• The 16/8 method: An 8-hour eating window followed by 16 hours of fasting, often achieved by skipping breakfast.

• Eat-stop-eat: Fasting for 24 hours once or twice a week.

• The 5:2 diet: Eating only 500–600 calories on two nonconsecutive days each week, with regular eating on the other five days.

IF often leads to reduced calorie intake, which can help with weight loss over time. Calorie-free drinks like water and black coffee are allowed during fasting.

In a recent study, 60 healthy people aged 48 to 52 were divided into two groups: one group practised alternate-day fasting (ADF) for four weeks, while the other ate usually. ADF participants fasted for 36 hours, followed by 12 hours of eating, which led to a calorie reduction of 37.4%. The ADF group saw improvements in body composition, with BMI decreasing by more than 1 kg/m², and better cardiovascular health, such as lower blood pressure and heart rate. The Framingham risk score showed a 1.42% reduced risk of future cardiovascular issues. Long-term ADF also improved cholesterol and thyroid function, reduced inflammation, and lowered the ageing-related amino acid methionine level. Another study involving 24 older adults (aged 55 to 79) explored time-restricted feeding (TRF), where participants fasted for 36 hours, followed by 12 hours of eating over six weeks. TRF reduced hunger and slightly lowered heart rate but did not significantly affect cardiovascular health or inflammation.

A note on safety: Before starting intermittent fasting (IF), it’s essential to consult a healthcare professional, especially if you have pre-existing conditions like diabetes, heart disease, or a history of eating disorders. IF may not be suitable for pregnant or breastfeeding women, individuals with certain metabolic issues, or those underweight. It’s crucial to ease into the practice, starting with shorter fasting periods and gradually increasing duration. During fasting, stay hydrated by drinking water, herbal tea, or black coffee, and ensure you eat balanced, nutrient-dense meals during eating windows to prevent nutritional deficiencies. Listen to your body and stop if you experience dizziness, extreme fatigue, or other concerning symptoms.

Mediterranean Diet-the best eating style in the current time

The Mediterranean diet (MedDiet), commonly practised in Greece and Southern Italy, is known for being low in saturated fats and high in vegetable oils. It is one of the most well-documented diets for slowing the development of age-related diseases. This diet emphasizes consuming unrefined cereals, fruits, vegetables, legumes, and olive oil, along with a moderate intake of dairy and alcohol and limited meat consumption. It offers a combination of vital nutrients, antioxidants, and anti-inflammatory compounds that support healthy ageing.

A study involving 1279 participants aged 65 to 79, without chronic diseases, was split into intervention and control groups to examine the effects of a Mediterranean-style diet on ageing. After one year, participants in both Italy and Poland who followed the Mediterranean diet showed significant improvements in epigenetic age markers. Notably, Polish women experienced a "rejuvenation" effect, with reduced epigenetic age acceleration. A follow-up study of 612 participants from the same project showed that the Mediterranean diet positively impacted gut microbiota, reduced frailty, and improved cognitive function. It also lowered inflammation, with beneficial changes in producing healthy gut metabolites.

Medstyle eating is superior for managing ageing-related risk factors. Sarcopenia, a condition marked by the loss of muscle mass and strength with ageing, leads to decreased mobility and increased risk of falls and mortality. Preventing muscle loss is essential for healthy ageing. Research shows that adherence to the MedDiet can help reduce muscle mass decline and improve muscle function, particularly in older adults. The MedDiet, rich in fruits, vegetables, and cereals, provides anti-inflammatory and antioxidant nutrients, like vitamins C and E, which support muscle health. Studies suggest the diet may also balance acid-base levels, further protecting against sarcopenia. Ageing leads to the natural decline of bone tissue, which is more pronounced in postmenopausal women and can result in osteoporosis, a condition marked by low bone mass and increased fracture risk. While calcium and vitamin D are key nutrients for bone health, other vitamins (A, B, C, E, K), minerals (potassium, magnesium, silicon), and macronutrients also play essential roles. The Mediterranean diet (MedDiet) has been linked to higher bone mineral density (BMD) and lower fracture risk, particularly in women. Components like grains, fish, olive oil, and physical activity within the MedDiet contribute to better bone health. Further research is needed to explore these effects.

Cardiovascular diseases (CVD) are linked to chronic low-grade inflammation and oxidative stress. The Mediterranean diet (MedDiet) helps reduce CVD risk by lowering LDL cholesterol, improving insulin sensitivity, and decreasing inflammation. Rich in unsaturated fats and polyphenols, the MedDiet promotes heart health by controlling lipid levels and reducing blood pressure. Additionally, its anti-inflammatory properties prevent atherosclerosis and stabilize plaques that can cause strokes, making it effective in CVD prevention, especially in the elderly. Sexual health is crucial for healthy ageing and enhancing physical, emotional, and psychological well-being. The MedDiet has been shown to improve sexual performance in the elderly, with compounds from foods like citrus, peppers, and tomatoes helping counter erectile dysfunction, particularly in those with type 2 diabetes.

The diet has been shown to reduce the risk of cognitive decline and dementia. Studies suggest that high adherence to MedDiet, especially with the inclusion of extra-virgin olive oil (EVOO), improves cognitive function and reduces Alzheimer's risk. A diet rich in plant-based proteins, legumes, and unsaturated fats supports better brain health, making MedDiet an effective strategy to prevent age-related cognitive impairment. Ageing weakens the immune system, increasing the risk of infections, with micronutrient deficiencies playing a significant role. Essential vitamins and minerals like A, D, E, C, B6, B12, selenium, zinc, copper, and iron are crucial for immune health. Vitamin D, in particular, impacts immunity, but deficiency is expected in the elderly. The MedDiet, rich in nutrients, supports immune function, and studies show it positively affects gut microbiota, which plays a vital role in immune regulation. Probiotics and MedDiet adherence can reduce infection risks and improve the immune response in older adults.

Future direction in dietary interventions for healthy ageing

Dietary interventions hold great potential for promoting healthy ageing by influencing critical molecular pathways in the ageing process.

While current research shows promising results, further studies are needed to refine personalized nutritional strategies to improve healthspan and manage age-related conditions.

Future research will likely focus on chrononutrition, the effects of intermittent fasting, and specific diets like Mediterranean and DASH diets on chronic diseases, functional abilities, and the quality of life in older adults. Additionally, researchers aim to enhance tools for assessing the relationship between diet and healthy ageing, including developing new dietary assessment markers and improved methods for measuring ageing. Long-term studies will explore the effects of micronutrients and macronutrients across various life stages to build comprehensive dietary guidelines that promote healthy ageing.

How to age healthy? Take a look at your lifestyle now!

There are several ways to improve your biological age, and it’s never too late to start—even at 70 or beyond. However, starting early rips the maximum benefits. Here are some healthy ageing tips to support a more vibrant life as you age.

Get Moving: Regular physical activity improves mobility, prevents falls, and reduces disease risks. Exercise also enhances brain function, aiding in tasks like learning and problem-solving. Essential exercises include:

• Endurance (e.g., hiking, biking) for heart health.

• Strength (e.g., weightlifting) for muscle maintenance.

• Balance (e.g., tai chi) to reduce fall risk.

• Flexibility (e.g., yoga) to stay limber. Aim for 2.5 hours of exercise weekly.

Eat Healthy: A nutrient-rich diet promotes brain and body health. Focus on:

• Nutrient-rich foods like seafood, nuts, and lean meats.

• Fruits and vegetables—five servings daily.

• Portion control and moderation of unhealthy additives. A Mediterranean-style diet benefits heart and brain health.

• Try calorie restriction and intermittent fasting under the supervision of a qualified healthcare professional. Opt for ingredients used in a MedDiet.

Prioritize Physical Health:

• Limit alcohol and aim for 7–9 hours of sleep.

• Quit smoking and stay on top of health checkups.

Care for Mental Health:

• Manage stress through exercise, meditation, and socializing.

• Seek help if feeling down.

Nurture Relationships: Combat loneliness by volunteering, staying in touch with loved ones, and connecting with your community.

Engage Your Mind: Keep your brain active by learning new skills, visiting new places, and enjoying hobbies like reading or cooking.