How Much Exercise Do You Need?

An average-sized adult can walk for nearly half an hour on the energy in one medium apple. A slice of apple pie contains about six times that. You can do the arithmetic yourself, and the arithmetic is the whole problem.

Two different questions, two different answers

Almost every argument about exercise comes from collapsing two separate questions into one. They have genuinely different answers, and confusing them is why people conclude exercise “doesn’t work.”

How much for weight loss? Considerably more — and this is where honesty matters. Exercise alone, without changing what you eat, typically produces modest weight loss: often only one to two kilograms over months in controlled trials. The studies that achieve real loss through activity alone tend to use volumes most people cannot sustain.

That is not an argument against exercising. It is an argument for knowing what you are buying with it.

The change most people missed

One rule quietly disappeared from the guidelines and it is worth knowing about, because the old version stopped a lot of people before they started.

The previous guidance said aerobic activity only counted in bouts of at least ten minutes. That requirement was removed.¹ The evidence did not support it: activity of any duration counts toward the weekly total. Five minutes of stairs counts. A brisk seven-minute walk to the shop counts.

If you have been discounting everything short of a proper session, you have been under-counting your week. Start counting it.

My father, aged 86

Rather than abstractions, let me describe a real day. My father lives in a village in eastern Romania at the foothills of the Carpathians. He and my mother keep a garden, a cow, and hens, and he is an expert beekeeper. They grow most of what they eat.

His morning begins when the cow makes it clear she wants breakfast. That means a large pile of hay carried on a fork some thirty feet, and two buckets of water at roughly twenty pounds each — carried by hand. Then the cow is milked, by hand, which is one of the most demanding forearm workouts I have ever attempted. A cow producing twenty-odd litres a day needs a great deal of food and at least ten buckets of water, each carried a hundred feet. And there is the matter of the dung, which does not remove itself.

That is before the garden, and before the bees. It is not exercise. Nobody in that village would call it exercise. It is simply the day.

For most of human history nobody needed a plan to be physically active. The activity was the life. What we now call “exercise” is our attempt to reinstate by choice what circumstance used to impose.

My father is 86 and has never been to a gym. The comparison is not meant to shame anyone — almost none of us can restructure our lives that way. It is meant to calibrate. When we compare a thirty-minute walk against that baseline, it becomes obvious why the walk alone does not transform a waistline.

Why exercise still matters enormously for weight

Having been blunt about what exercise will not do, let me be equally clear about what it does.

• It is the single best predictor of keeping weight off. People who lose weight and maintain the loss are overwhelmingly people who stay active. Diet takes weight off; activity is what keeps it off.
• It protects muscle during weight loss. Lose weight without resistance training and a meaningful share of what you lose is muscle — which lowers your metabolic rate and makes regain easier. This is the strongest argument for lifting something heavy twice a week.
• The health benefits are largely independent of weight. Fitness improves cardiovascular risk, blood sugar, blood pressure, sleep and mood whether or not the scale moves. Aerobic capacity is among the strongest single predictors of survival we have — you can estimate yours with the Rockport walk test.

Where to actually start

If you are currently doing very little, the biggest health return in your life is available at the bottom of the curve. Going from nothing to twenty minutes most days buys more than going from forty-five minutes to an hour.

• Count what you already do. Use the activity calculator to see the real energy cost of what fills your week — the figures are usually sobering, and that is useful information.
• Walk faster rather than longer. Intensity moves the needle more than duration for the same time spent.
• Add resistance twice a week. Non-negotiable if you are over 50 or losing weight.
• Stop discounting short bouts. They count. They always did; the guidelines simply caught up.
• Expect exercise to earn its keep on the scale slowly, and let food do the heavier lifting there.