How to Prepare for an InBody Scan So the Reading Is Consistent
To prepare for an InBody scan, keep the conditions the same every time: scan in the morning, before training, without a large meal or a lot of fluid in the previous two to three hours, after using the toilet, in light clothing and with no hard exercise or heavy drinking the day before. The goal is not a flattering number. It is a number you can compare with the next one. The scanner reads how electrical current passes through the water in your body, so anything that shifts your water balance shifts the result. Control those variables and changes between scans reflect real changes in muscle and fat.
Why preparation matters more than the machine
An InBody uses bioelectrical impedance: a small, painless current passes through your body via the hand and foot electrodes. Lean tissue holds a lot of water and conducts well; fat holds little and resists. From that resistance, the machine estimates total body water and then muscle and fat. The full explanation is in what an InBody scan is.
The weak point is obvious once you see it. The machine measures water and infers everything else. If you are dehydrated after a long run, or carrying extra fluid after a salty meal, the inference shifts. A difference of a kilo or so in apparent muscle between two scans can come entirely from conditions on the day. Good preparation turns that noise into something close to background.
The 24-hour routine
This is the routine I give clients before a scan in the studio. It is the same each time, which is the whole point.
The day before
- No hard training. A heavy leg session or long run the day before can affect fluid in your muscles. A walk is fine.
- Keep alcohol minimal, ideally none. It affects hydration in both directions over the following day.
- Eat normally. Not an unusually salty takeaway, not a dramatically low-carbohydrate day. Both change how much water you hold.
- Drink your usual amount of water. Do not “flush” with extra litres, and do not cut back.
The morning of the scan
- Scan before you train. Exercise raises body temperature and moves fluid around. If your session follows the scan, that is ideal.
- Hold off on breakfast and big drinks for two to three hours. Food and fluid in your stomach add weight the machine has to account for. If you must eat, keep it small and identical each time.
- Use the toilet beforehand. A full bladder adds weight and water that is not part of you.
- Skip the hot shower or bath right before. Heat changes circulation and skin temperature.
- Wear light clothing, the same kind each time, and take off watches, rings and anything metal you can easily remove.
- Stand for a few minutes before stepping on. Fluid shifts when you go from lying or sitting to standing. Walking from the station is enough.
The quick checklist
If you only remember one thing, remember this list. Same:
- Time of day
- Food and drink timing
- Training timing (scan first)
- Clothing
- Toilet before
- Part of your menstrual cycle, where relevant
Things people do not realise affect the reading
Your menstrual cycle
Many women retain more water in the days before a period. That can nudge weight and body water up and make the scan look worse than it is. If your cycle is regular, scanning at the same point in it each time removes a big source of noise. If it is not, we simply note it on the printout and read the trend with that in mind.
Creatine
Creatine draws water into muscle, which can raise the lean mass reading in the first weeks of taking it. That is not fake, exactly, but it is not new muscle either. If you start or stop creatine between scans, tell your trainer. Our beginner’s guide to creatine explains the effect.
Travel and long flights
Flying, especially long haul, tends to leave you dehydrated and puffy at the same time. Give it a day or two after landing before scanning.
Illness
Fever, a stomach bug or a heavy cold changes fluid balance. Postpone the scan.
Recent changes in carbohydrate intake
Your body stores carbohydrate with water. A week of low-carb eating can make you look lighter with less “muscle”; a carb-heavy week the reverse. Neither reflects much real change.
What to do if you could not follow the routine
Life gets in the way. You trained the night before, or you had breakfast because you forgot. You have two sensible options.
- Rebook. If the scan is a key checkpoint, such as the end of a twelve-week block, it is worth moving it by a day or two.
- Scan anyway and annotate. Write down what was different. When you read the results, give that scan less weight and lean on the ones either side of it.
What not to do is scan twice in quick succession hoping for a better number, or compare a scan taken after lunch with one taken first thing. That way lies false conclusions.
Who should not have a scan
Because the scan passes a small current through the body, people with a pacemaker or other implanted electronic medical device should not be scanned. Pregnancy is another reason to skip it, as the readings are not designed for it. If you have a medical condition that affects fluid balance, such as kidney or heart disease, or take medication like diuretics, talk to your GP first, and expect the numbers to be less reliable. The manufacturer publishes its own guidance on taking an InBody test, which is consistent with the routine above.
How often to scan, and how we use it
Real change in muscle and fat is slow. Every four to eight weeks is plenty for most goals; more often and you are mostly measuring water. The timing question has its own post, how often to measure body composition.
In the studio, scans are booked at the start of a session, before any training, at roughly the same time of day as your previous one. We read the trend over several scans rather than reacting to any single sheet, and we combine it with things that cannot be faked: the weights you lift, how your clothes fit, how you feel. If you want to know what the numbers on the printout mean, see how to read your InBody results. The scanner is part of 1-1 personal training at the Highgate studio, not a standalone service.
Questions we get asked
Can I drink water before an InBody scan?
A few sips are fine. Avoid drinking a large amount in the couple of hours beforehand, and keep your hydration the day before normal.
Can I have coffee before the scan?
A small black coffee is unlikely to matter much, but it is a drink and it can send you to the toilet. Whatever you choose, do the same thing every time.
Why did my results change so much in one week?
Almost always water: a different time of day, a heavy session, a salty dinner or a change in carbohydrate intake. Real muscle or fat changes of that size do not happen in a week.
Do I need to do anything special on the day I start training?
No. If you would like a baseline scan at your first personal training session, just follow the morning routine above. More about the studio is on The Highgate House homepage.
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