• InBody Scanner: Is it accurate for tracking fat loss results?

    By The W10 Team

    Did you really just put on 6% body fat in a couple of days?

    Why an understanding of the InBody scanner will help you understand fluctuations in its results.

    Here at W10 Personal Training Gym we use the InBody machine as a way to measure body composition in order for clients to track their progress, namely through muscle mass and body fat %.

    While it is one of the more accurate body scanners on the market, its findings shouldn’t be taken as gospel. As with all measuring tools, there are surrounding factors that can have an influence on the reading taken at the time.

    So before you freak out when you next step on the scanner, as your results show a different story from what you had expected, this article gives you insight into how it works and the factors that can affect the reading (positively and negatively).

    Understanding the context for future scans will make knowledge and interpretation clearer.

    How the InBody scanner works

    The InBody uses BIA (Bioelectrical Impedance Analysis) technology, which measures “total body water” by reading the impedance (resistance) of low level currents through the body. Therefore, temporary changes in the body can result in temporary changes in body composition results.

    Once you understand how the readings can change in such a short space of time, you’ll see why just one snap shot scan doesn’t always tell the full story.

    Factors to consider when interpreting your InBody stats:


    Depending on whether you weigh in before or after working out, will have an influence on the results, especially the body fat % reading. 
During exercise water is concentrated to the exercised area to supply nutrients and remove waste products. After exercise, impedance decreases and so does body fat – i.e. you will look leaner after you train. Additionally your body temperature increases when you exercise which again reduces impedance and decreases body fat %.

    Body temperature 

    If the body is exposed to warmer temperatures, the skin temperature increases and body fat % decreases. 
Generally lower body temperature means an increase in impedance, which means lower fat free mass (i.e. less muscle, more fat). A study showed that sauna exposure increased body temperature and caused a 1.7-3.2% reduction in body fat. And after being in an icy room, body temperature decreased and body fat increased by 1.3-4.2%. And while body temperature from the cold exposure returned to normal after 30 mins, body fat % did not return to a stable state even an hour after cold exposure.

    So bear this in mind if you’ve just trained or been in a warm environment, you’re likely going to have lower body fat and on the flip side, if you’ve just been outside and haven’t had time to warm up, your body fat % might appear increased.

    Taking a shower or bath

    This increases blood flow and decreases impedance and so body fat % again decreases. A study showed that taking a shower before getting on the scanner resulted in a reduction in weight and body fat. From this study, one lady over a period of 7 days lost overall weight and body fat % (0.1kg-0.7kg and 0.5%-1.9% respectively)

    So if you’ve just had a shower, chances are you’ll be lighter and leaner.


    Eating decreases impedance through the ingestion and digestion of food. A study showed with meals eaten over the course of the day impedance is impacted and body fat influenced by up to 8.8% for females and 9.9% males.

    The more you eat over the course of the day, the more chance you have of the reading not showing a true reflection of the results in front of you.

Clothing, and faeces / urine do not affect impedance (resistance), and are considered as fat mass as electricity does not flow through them. So if you haven’t been to the toilet you’ll get a different measurement compared to scanning after going to the toilet.

    Body fat decreases immediately after going to the toilet (reduced body weight used as the amount of fat mass). So consider this too as a factor.


    Ladies, your results will have a larger variability than men due to periods. Weight is increased in the luteal phase (day 14 onwards in cycle) due to accumulation of total body water (increase in progesterone). This results in a decrease in body fat %.

    However, diet at this time (increased sweet / salty food cravings) may cause accumulation of fat mass, increasing body fat %.

    Therefore, weight and body fat can change quite a bit during the luteal and menstrual phase. Changes are so individual so it’s best not to scan during luteal / menstrual phase and try to scan when in the follicular phase (day 1-14 of cycle) if possible.


    Weight is a big factor in total body water. For the most accurate results it’s better to remove clothing and ensure no food is ingested (fasted is best) and you’ve been to the toilet. i.e. with clothes body fat % will increase.

    So in an ideal scenario, you would do the scan without any clothes on, fasted and when you’ve been to the toilet – and for women only when you’re in the follicular phase of your cycle.

    However, in practical terms this isn’t always possible. Therefore you just need to have the factors outlined above in your mind as you're stepping on to be scanned.

    If your results have taken a sudden turn for the worse, it might not be that you’ve put on all that body fat in a short space of time (and equally you probably haven’t gained 3kg of muscle in a week either!)

    The best way forward is to try and be as consistent as possible with the scans (time of day / when you’ve eaten / time of the month etc.) in order to get as accurate of a measure as possible.

    And when interpreting the results, look for overall patterns and trends rather than single scans in isolation.


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Set up in 2009 by founder Jean-Claude Vacassin (a regular health and fitness contributor to the Daily Telegraph) the W10 Performance gym is located in West London at 202-208 Kensal Road, London W10 5BN. W10’s Gym memberships offer personal training, nutrition advice, yoga, boxing, HITT and other functional fitness classes. They also have physio and sports massage practitioners onsite. They are proud to offer a high level of fitness to residents and local workers in Kensal Rise, Kensal Green, Queens Park, Willesden, Kilburn, Harlesden, Ladbroke Grove, Notting Hill, Kensington and Westbourne Park areas.


Find us The Basement, 202-208 Kensal Road, London W10 5BN

Call us on 020 3489 5428