MET (Metabolic Equivalent of Task)

MET: what is it?

METs exist to solve a comparison problem: how do you put swimming, gardening, a spin class and a desk job on the same scale? By expressing every activity as a multiple of resting metabolism. The reference value, 1 MET, is defined as 3.5 ml of oxygen per kg per minute, which works out to roughly 1 kcal per kg of bodyweight per hour. That second equivalence is what makes METs practical: it turns any activity, any duration and any bodyweight into a calorie estimate with one multiplication.

The calculation

Energy expenditure in kilocalories equals METs multiplied by bodyweight in kilograms multiplied by duration in hours. A 70 kg client doing 45 minutes of an activity rated at 8 METs burns approximately 8 x 70 x 0.75, which is 420 kcal.

One caveat matters for anyone doing serious calorie maths. That figure is total energy expenditure for the period, which includes the resting energy the client would have burned anyway. If you are adding exercise on top of a maintenance calorie estimate that already accounts for rest, you are double-counting roughly one MET-hour. For most coaching decisions the difference is small enough to ignore; for a tightly controlled deficit it is not.

Typical MET values

Published compendia list MET values for hundreds of activities. The values below are the widely used typical figures; individual cost varies with skill, terrain, equipment and how hard the person is actually working.

Where METs are genuinely useful

Three places. First, comparing activities for a client choosing how to spend their week - seeing that brisk walking sits near 4 METs and a moderate bike ride near 7 reframes what counts as useful movement. Second, estimating the energy side of a nutrition plan when a client has no wearable. Third, understanding public health guidance, which is written in MET-minutes per week; the standard target of 150 minutes of moderate activity translates into a MET-minute figure that lets any combination of activities count toward it.

They also give you a plain-language ceiling. A client whose functional capacity is around 4 METs cannot comfortably climb two flights of stairs carrying shopping, and that is a far more motivating framing than any percentage.

• MET values are population averages, not individual measurements.
• They ignore fitness level: the same activity costs the fit and unfit client the same MET rating, though not the same effort.
• They ignore excess post-exercise oxygen consumption entirely.
• For intermittent work like circuits or HYROX, a single MET value badly misrepresents the session.

The limits to be honest about

The 3.5 ml/kg/min definition of one MET is itself an approximation of average resting metabolism. Real resting values differ with age, sex, body composition and lean mass, and older or heavier individuals typically sit below 3.5, meaning a MET-based estimate overstates their expenditure.

None of this makes METs useless. It makes them a planning tool rather than a measuring tool. Use them to compare options and set expectations; use body weight trend and food logs to actually verify what is happening.