Why People in Their Mid-40s Gain Body Fat
The internet is a confusing place. Its hard to know where to go and trust the information that is easily available. It can also be disheartening at times when you don’t understand the facts behind certain situations. One such scenario, is people in the mid-40s who gain body fat.
Here are some facts that can help us better understand why we gain those extra few pounds
1. Hormonal Changes
Estrogen/Testosterone decline:
In women, perimenopause begins (as early as 40), causing estrogen levels to drop, which promotes fat accumulation, especially visceral fat [Lovejoy et al., 2008].
In men, testosterone declines ~1% per year after age 30, impairing muscle maintenance and increasing fat mass [Harman et al., 2001].
2. Reduced Resting Metabolic Rate (RMR)
Muscle mass decreases with age (sarcopenia), lowering daily energy needs.
RMR can drop by 1–2% per decade after 30 [Roberts & Rosenberg, 2006].
Less lean mass = fewer calories burned at rest.
3. Increased Insulin Resistance
With age, the body becomes more insulin resistant, particularly with poor diet and low activity.
This promotes fat storage and impairs fat oxidation [Chang & Halter, 2003].
4. Lifestyle Changes
More sedentary jobs, reduced NEAT (non-exercise activity thermogenesis), and less structured exercise.
Time constraints (career, family) reduce exercise and meal prep.
5. Chronic Stress & Cortisol
High stress in 40s (work, finances, caregiving) raises cortisol, which increases appetite and central fat deposition [Epel et al., 2000].
6. Sleep Disruption
Hormonal changes and lifestyle stress often reduce sleep quality.
Short sleep (<6 hrs) is linked with greater fat gain and impaired glucose regulation [Spiegel et al., 2004].
So if you are in your mid-40s and are struggling right now, keep the head up. Everyone that goes through this phase will find maintaining their body composition from earlier years really difficult. But know that there is modifiable factors that we can work on such as strength training, good sleep hygiene and a healthy diet.