Energy & Immunity After 40: What Changes in Men vs Women

19 March 2026

Author: Dr. Bhanu Sharma

Turning 40 is a life-defining moment. It is a time when the body begins to undergo subtle changes. Eyesight may begin to decline, and both energy and immunity both weaken. This progression is natural but may not manifest in the same way for men and women. Hormones, metabolism, stress and the ageing process itself affect each gender differently.

From an Ayurvedic standpoint, this phase marks a gradual shift towards Vata Dosha* (bio-energy) dominance, which influences ojas (vitality), bala (strength) and immune stability. Understanding these changes helps individuals navigate the period more effectively and sustain well-being into the later years.

Vata Dosha: This governs circulation, nerve impulses, and breath – when imbalanced it can cause anxiety, dryness, pain, and irregular digestion.

Why Energy Levels Drop After 40

Before exploring this further, we must first understand: What is energy? Energy may be defined as the body’s capacity to perform physical and mental tasks. Ayurveda believes it depends on agni (digestive fire), bala (strength), and utsaha (vital enthusiasm).
The 6th-century Ayurvedic physician Sushruta stated that ageing is not a disease but a natural process, much like thirst, hunger, sleep, and death.

 In Ayurveda, life stages are clearly classified:

• Balyavastha (childhood): up to 16 years
• Vriddhi (growth): up to 20 years
• Youvana (youth): 21–30 years
• Sampurna (complete development): 31–40 years
• Hani (decline): 41–70 years
• Madhyavastha (middle age): 16–70 years (Kshirapa, Kshirannada, Annada)
• Vruddha Vaya (old age): 71–100 years

According to the Sharangadhara Samhita, a classical text, one faculty declines most significantly with each decade of life. These faculties include balya (childhood vitality), vriddhi (growth), chhavi (radiance), medha (intellect), twak (skin quality), drishti (vision), shukra (reproductive vitality), vikrama (physical strength), buddhi (wisdom), and karmendriya (functional efficiency of the organs of action).

Metabolic Changes

Metabolism is governed by agni (digestive fire), including Jatharagni, Bhutagni, and Dhatvagni*. With increasing Vata Dosha, agni may become irregular (called vishamagni).

* Jatharagni (primary digestive fire in the stomach and gut);  Bhutagni (elemental metabolic fire acting at the level of the five elements); Dhatvagni (tissue-level metabolic fire responsible for nourishment of the dhatus).

This irregularity may present as Mandagni (low digestive fire), leading to the formation of ama (toxins)

• Tikshnagni (digestive imbalance marked by excessive thirst and internal heat) is associated with dhatu kshaya (tissue depletion) and bala kshaya (loss of strength)

Ama causes srotorodha (blockage of body channels), reducing nutrient supply and contributing to fatigue.

Modern science explains this in terms of reduced mitochondrial efficiency, slower recovery, and increased energy depletion.

Hormonal Shifts

Hormonal fluctuations begin happening in midlife. In Ayurveda, this connects with a decline in Shukra Dhatu (reproductive tissue) and reduced veerya (vital strength). Manifestations at this time include: hormonal fluctuations, especially in women, disturbed sleep, increased fatigue and temperature fluctuations.

Muscle & Recovery Changes

After a person gains full maturity, food goes to maintain tissues, rather than build them up. This leads to a decline in muscle strength. Modern science corroborates this, stating that muscle loss begins from the late 30s – this is accompanied by slower stress recovery.

How Immunity Changes with Age

What is Immunity? It is the body’s ability to prevent and fight infections and abnormal cells. Ayurveda lists three factors for a healthy immune system: Ojas (vital essence of immunity), balanced agni (digestive fire), and nourished dhatus (body tissues).

Ayurveda states that with age, there is a decline of Kalaja Bala (age-related natural immunity). This shows up in:

• Ojas kshaya (depletion of vital essence)
• Weakening of Rasadi Dhatus*
• Irregular agni

*Rasadi Dhatus: Body tissues beginning with rasa or nutritive fluid.

 Slower Immune Response

With age, certain conditions develop naturally: Immune cell activity reduces, healing slows, and defence responses are delayed. These conditions reflect declining ojas, weaker dhatus, and unstable agni – all leading back to slower immune responses.

 Increased Inflammation

Well-functioning agni maintains vitality.

Age leads to increased Vata, which may deplete agni, resulting in ama (toxin) accumulation. The toxins circulate in the system, causing inflammation and tissue degeneration.

Stress and Immune Balance

Ageing reduces stress tolerance.

Stress causes:

• Vata vriddhi (increased Vata)
• Ojas kshaya (depleted vitality)
• Further disturbance of agni

This weakens immune balance, reduces the capacity to process stress, and increases disease susceptibility.

Differences in Men vs Women After 40

After 40, women enter Rajonivritti Kala (menopausal phase), while men experience a gradual decline in the male hormone testosterone, often referred to as andropause.

Hormone Patterns

In women this period is termed menopause and marked by several changes:

 Physiology:

• Sharp fall in estrogen and progesterone (female hormones)
• Ovaries stop releasing ova
• End of menstruation (12 months confirms menopause)
• Happens between 45–55 years in most cases

Ayurvedic view:

• Vata vriddhi* (increased Vata bio-energy) with possible Pitta* (bio-energy) imbalance
• Dhatu kshaya (tissue depletion)

*Vata governs movement and nerve activity; Pitta governs metabolism and transformation.

This condition may manifest as hot flashes, night sweats, vaginal dryness, mood swings, reduced bone density, weight gain, and an increased risk of heart complications. The condition is universal, and the symptoms are likely to show abruptly.

Men may also undergo a gradual age-related testosterone decline of approximately 1% per year after 40.

Physiology:

• Slow reduction in testosterone
• Testes function continues
• Fertility may persist
• Usually, symptoms show up after 50

The condition may manifest in reduced libido, fatigue, muscle loss, mood changes, and reduced bone density. It is not universal and is likely to be gradual.

Energy Needs

In women, faster dhatu (tissue) depletion happens especially Asthi Dhatu (bone tissue) and Mamsa Dhatu (muscle tissue). Along with rising Vata, reduces strength and energy more sharply after menopause.

In men, hormonal decline is slower, so muscle and stamina reduce gradually, though falling testosterone eventually affects strength and recovery.

Immune Vulnerability Differences

Here are symptoms that show up in women:

• Immunity imbalance caused by the sudden hormonal drop
• Faster depletion of ojas (vitality) due to accelerated depletion of tissues

In men, the situation is somewhat different: