Metabolism

Losing energy and strength in your 40s? Why muscle is your metabolic engine

By Dr Lwin, GP and lifestyle medicine physician · Last reviewed October 2026

Quick answer

Muscle is the largest place your body stores and uses blood sugar, so keeping it is one of the best things you can do for your metabolism. In the DARE randomised trial of 251 adults with type 2 diabetes, both aerobic and resistance training lowered HbA1c, and doing both together lowered it the most.

In your twenties, energy felt free. In your forties, the stairs feel steeper, your jeans fit differently and recovery takes longer. Much of that change comes from losing muscle, quietly, year after year, especially when work keeps you seated.

Why muscle matters for metabolism

After a meal, your muscles take up much of the glucose in your blood. More active muscle means more space to store that energy and less strain on insulin. Muscle also supports balance, posture and independence as you age.

The good news: muscle responds to training at any age. It is never too late to build it.

What the DARE trial showed

In the DARE trial (Annals of Internal Medicine, 2007), 251 inactive adults with type 2 diabetes aged 39–70 were randomly assigned to aerobic training, resistance training, both, or no exercise for 22 weeks, three times a week.

Aerobic training: lowered HbA1c by about 0.5 percentage points compared with no exercise (source).
Resistance training: also lowered HbA1c compared with no exercise.
Both together: gave the biggest improvement. The combined group also exercised for longer overall, which partly explains the extra benefit.

What most people miss

Most busy professionals pick one type of exercise. Runners skip weights. Gym-goers skip cardio. The DARE results suggest your metabolism does best with both. The British Society of Lifestyle Medicine lists physical activity as one of six pillars of health for this reason: it touches blood sugar, mood, sleep and heart health at once.

And strength training does not have to mean heavy barbells. Body-weight exercises and resistance bands count.

A 20-minute starter routine

Do this two or three times a week, on days you also walk briskly:

Squats to a chair: 3 sets of 10.
Wall or desk press-ups: 3 sets of 10.
Resistance band rows: 3 sets of 12.
Step-ups on a stair: 3 sets of 10 each leg.
Plank: 3 holds of 20–30 seconds.

Increase the challenge a little every two weeks: more repetitions, a slower tempo or a stronger band.

FAQs

I'm over 50. Is strength training safe? For most people, yes. Start light and build up. Speak to your doctor first if you have heart, joint or blood pressure problems.

Will weights make me bulky? No. At this level, training mainly makes muscle stronger and healthier, not much larger.

Does walking count? Yes, brisk walking is aerobic exercise. Combining it with strength work gives the most benefit.

For the years that matter, Dr Lwin

This article is general education, not personal medical advice. If you have symptoms or concerns, speak to your GP.