A woman training with a medicine ball in a busy neighbourhood gym

Losing weight is not the same as losing fat

Breathe into Rysflo each morning. It measures whether you are burning fat or still running on carbohydrate, then sets the day’s meals and macros — protein, carbs, fat and fibre in grams — so you eat for the day you are actually having.

Lose fat with Rysflo
$29 / month AI meal plans HIPAA compliant

What the scale cannot tell you

Four failures hiding inside a single number.

Fat, or lean mass

A deficit costs you lean tissue as well as fat, and that is true of caloric restriction and of a GLP-1 alike.1 The scale adds the two together and reports the total.

Water, not fat

Every gram of stored glycogen holds roughly three grams of water with it. Emptying those stores takes a kilo or two off in the first week with almost no change in fat — which is why nearly every diet appears to work at the start.

Buried under the noise

Sodium, hydration and gut contents move daily weight by a kilo or more, which is larger than a good week of actual fat loss. The trend only clears the noise after a fortnight of weigh-ins.

A number with no cause

Four different days can produce the same reading. The scale cannot tell you which of them you had, so it cannot tell you what to change.

How your breath knows

Three steps, and the last one is the reason a breath can tell you anything at all.

You eat

Food becomes glucose in the blood, and whatever is not needed is stored as fat. Your body runs on one or the other at any moment.

You burn stored fat

Burn it steadily and it breaks down faster than your cells can use it up. The liver packs the surplus into ketones.

You breathe it out

One of those ketones falls apart into acetone, which is small enough to cross into your lungs and leave on the next breath. That is what Rysflo reads.

A woman talking with her clinician in a consulting room

On a GLP-1, this matters more

Semaglutide and tirzepatide produce the largest weight losses available, and lean mass comes down alongside the fat.1 In one study of patients with obesity, fat mass fell 18 per cent over twelve months while lean mass dropped early and then stabilised, and grip strength improved.3

A daily reading gives you evidence of whether fat is being oxidised at all — something to weigh that falling number against, which on a GLP-1 is the difference between getting lighter and getting weaker. Neither a weigh-in nor a reading separates the two curves by itself.

If you prescribe GLP-1s
A trainer and client reviewing breath readings together on a phone

With a trainer, it stops being guesswork

A trainer sees you for two hours in a week and has to infer the other 166. Share your readings and they can see whether you are actually burning fat, whether the meals landed, and whether you drifted — before the next weigh-in tells them.

You keep control of it. Give access, and withdraw it, whenever you like.

If you coach clients

What you get for sixty seconds a day

Most weight loss plans are built from your height, weight and age. Yours is built from your own daily metabolic reading.

Protein set high enough to protect muscle

A man at the bottom of a goblet squat
3.2 ppmacetone this morning
165 gprotein today

Eat enough to keep losing fat

A bowl of avocado, soft-boiled egg, chicken and greens

Know which days you burned fat

A new plan every morning

Today’s targets
2,100kcal today
Protein165 g
Carbohydrate180 g
Fat80 g

Know if the plan is working in week two, not week six

Progress card
Heads up. Your trend has been flat since week 2
target range 1006020 wk 1wk 2wk 6

One breath a day, no food diary

A woman holding the Rysflo breath device and reading her result on her phone
06:42reading taken
58sstart to result

What changes, and when

Fat loss is slow and the scale is noisy. The reading is neither — here is what it actually gives you, and when.

  1. Week 1

    A baseline, not a verdict

    Readings move day to day, and that spread is the point: it is your range, not a population’s. Nothing to change yet. Eat as you normally do so the baseline is honest.

  2. Weeks 2–3

    The pattern appears

    You can see which days the switch happens and which days it does not, and what those days had in common. Targets start adjusting to what your metabolism is actually doing rather than to a formula.

  3. Weeks 4–6

    The answer to the question you started with

    Enough readings to separate signal from noise. Your weigh-ins now read against the fat-oxidation trend, so a flat week on the scale is either a plan that is not landing or a plan that is working while the scale hides it — and the readings tell you which of those is more likely.

Rates of fat loss vary with the person, the deficit and the plan. Rysflo measures what is happening; it does not set how fast it happens.

Take the first reading tomorrow morning

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Questions people ask

How soon will I see something useful?

The first reading gives you a number on day one, but a single reading is a snapshot. The useful part is the run: about two weeks before a pattern is legible, and four to six before it can settle an argument about whether a plan is working.

I have counted calories before and it stopped working. Why would this be different?

Calorie counting estimates the input and assumes the output. It cannot see that your metabolism has adapted, that the deficit is now costing lean tissue, or that a meal fermented rather than absorbed. Those are the three ways a disciplined week produces nothing, and they are the three things a reading can see.

Do I have to change what I eat?

Not to start. Take the reading, eat as you normally would, and let the first week establish a baseline. The daily targets come from your own readings, so the changes it asks for are the ones your data supports rather than a diet applied from outside.

What if the reading does not move?

That is a result, not a failure. A flat acetone week means the plan is not producing the fat oxidation you assumed it was — which is worth knowing in week two rather than after a month of weigh-ins that could not tell you why.

Do I have to fast before a reading?

No special fast. The reading is taken first thing, before coffee or food, which means the overnight gap has already done the work. Sixty seconds, then breakfast.

Is it accurate enough to act on?

For direction of travel, yes. For a precise rate of fat loss, no. Across the published studies, breath acetone explains about 77 per cent of the variance in blood beta-hydroxybutyrate (R² = 0.77) — strong enough to tell you which state you are in, not exact enough to tell you the grams. The measured limits are on the science page.

Sources

  1. GLP-1 receptor agonists induce loss of lean mass: so does caloric restriction — PubMed 40771503.
  2. Breath acetone correlates with capillary beta-hydroxybutyrate in type 1 diabetes — PMC12014577.
  3. Impact of semaglutide on fat mass, lean mass and muscle function in patients with obesity (SEMALEAN) — PMC12673431.

These studies describe caloric restriction and GLP-1 therapy. They are not studies of Rysflo, and none tested the three-analyte protocol as an intervention. What is established, and what is not.

Disclaimer: Rysflo is a metabolic tracker and measurement device intended for general wellness use. It does not cause weight loss, treat obesity, or replace clinical assessment — it measures what your metabolism is doing so the plan you are following can be judged on evidence rather than on the scale alone.

Lose fat, not just weight

At just $29 a month, device included. 30 days to change your mind, full refund.

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