Alice Turing
Reaching your 40s can bring subtle changes to how you feel throughout the day. You may find that a demanding workday leaves you more drained than it once did, or that recovering from exercise takes longer than expected.
It can be tempting to attribute these changes entirely to age, particularly when they develop gradually. However, persistent changes in energy can sometimes provide useful clues about what is happening beneath the surface.
Hormones, cardiovascular health, metabolic function, sleep, nutrition, physical activity, and stress can all influence how energetic you feel. Yet, many men never pay attention to them. In this article, let’s look at why you should start being more perceptive as you age above 40.
Your Energy Reflects Changes Happening Beneath the Surface
Energy levels can provide a broad indication of how your body is functioning, particularly when a noticeable change develops alongside other symptoms. You may find that a reduction in energy may coincide with changes in hormone levels, muscle mass, cardiovascular health, metabolism, or sleep. That does not mean fatigue can tell you exactly what is wrong, but it can be a useful reason to look more closely at your health.
Testosterone tends to be one hormone worth understanding as you move through midlife. It plays an important role in libido and muscle mass and can influence several aspects of physical function. However, very few men actually decide to check if their levels have changed over the years.
In a 2025 BMJ Open survey of 973 men, 49% scored as likely to have testosterone deficiency, but only 5% had been formally diagnosed. Men over 50 had 1.54–2.0 times higher odds than men under 40.
As Limitless Regen explains, low testosterone doesn’t really announce itself. It often disguises itself as a rough patch or a season in life. So, if you were used to pushing through discomfort in the past, you are already used to ignoring signs your body is giving you. This somewhat explains why people don’t think to test themselves. Yet, the older you get, the more seriously you want to start taking changes in energy.
Cardiovascular, Metabolic Health, and Hypertension Risks
You might wonder what’s so bad about a little fatigue caused by low testosterone levels. The answer is that fatigue has a correlation with other health risks. In a 2025 study of 4,349 participants, 48.7% reported fatigue. It noted that fatigue was significantly associated with advanced cardiovascular–kidney–metabolic syndrome, especially in young and middle-aged adults.
Even if your testosterone levels are normal, there are other aspects to also take more seriously, like blood pressure. As data from the CDC shows, hypertension in men between 40 and 59 was close to 56%. That’s a 26% increase compared to men between the ages of 18 and 39. Even when compared against women between 40 and 59, hypertension in men was still ~7% higher.
Hypertension can exist without obvious symptoms, so how energetic you feel is not a reliable way to determine whether your cardiovascular health is in good shape. Thus, you want to ensure you are getting regular health checks to assess blood pressure, blood glucose, and cholesterol.
The “Energy” Problem May Actually Be a Metabolic Problem
Changes in energy during your 40s can also coincide with gradual shifts in metabolism, activity levels, and body composition. Men may become less physically active because of demanding jobs, family responsibilities, or changes in their routines, while their eating habits remain largely unchanged. Over time, this can make maintaining muscle and a healthy body weight more difficult.
According to Dr. Natalie Barclay, testosterone is a key metabolic hormone that affects libido and muscle mass. However, in their 40s, testosterone in men starts to decline, as does metabolic rate. This is why men need to reduce their intake of liquid calories and fast food. In addition, Dr. Barclay recommends aiming for 150 minutes of moderate exercise per week.
This advice highlights an important part of the energy equation. A gradual reduction in physical activity can contribute to lower fitness and muscle mass, while calorie-dense foods and drinks can make weight gain easier. The result can be a cycle in which physical activity feels increasingly demanding, encouraging even more inactivity.
Regular movement helps interrupt that pattern. Aerobic exercise can be a great way to support cardiovascular fitness, while resistance training provides an important stimulus for maintaining muscle. At the same time, don’t neglect nutrition.
Still, lifestyle changes should not be used to explain persistent or unexplained fatigue. When a major change in energy continues despite reasonable improvements to sleep, nutrition, and activity, it is worth considering whether another factor may be involved.
Frequently Asked Questions
What blood tests should men over 40 have for fatigue?
Depending on your symptoms, a doctor may consider tests such as a complete blood count, thyroid function, blood glucose, kidney and liver function, vitamin B12, iron levels, and testosterone. The appropriate tests vary from person to person, so persistent fatigue is best evaluated individually.
What are the signs that fatigue is more than normal aging?
Fatigue deserves more attention when it is persistent, worsening, or noticeably different from your usual energy levels. It may also warrant evaluation when accompanied by unexplained weight changes, reduced exercise tolerance, breathlessness, dizziness, sleep problems, changes in libido, or difficulties managing everyday activities.
Can strength training improve energy levels after 40?
Yes, strength training can support energy levels by helping maintain muscle mass, physical fitness, and everyday strength as you age. It can also make routine activities feel less demanding. Start gradually and prioritize consistent training, adequate recovery, and proper technique rather than trying to lift as heavily as possible.
Key Numbers & Facts at a Glance
|
Percentage of men likely to have testosterone deficiency |
49% |
|
Percentage of men formally diagnosed with testosterone deficiency |
5% |
|
Increased odds of testosterone deficiency among men over 50 vs. under 40 |
Between 1.5 and 2x |
|
Recommended moderate exercise |
150 minutes/week |
|
Percentage of men aged 40–59 with hypertension |
~56% |
Changes in energy do not automatically signal a health problem, and feeling somewhat different in your 40s is not unusual. However, a persistent decline deserves more attention when it represents a clear change from your normal baseline. This is also true when it appears alongside changes in strength, libido, weight, sleep, exercise tolerance, or other aspects of your health.
The point is to not let a noticeable change go by unchecked. Use it as a reason to take stock of your overall health and discuss persistent or unexplained symptoms with a healthcare professional. Paying attention like this helps you recognize changes in how your body is functioning while there is still an opportunity to investigate contributing factors.
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I'm Alice and I live with a dizzying assortment of invisible disabilities, including ADHD and fibromyalgia. I write to raise awareness and end the stigma surrounding mental and chronic illnesses of all kinds.
