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If you’ve ever felt a bit confused by the number you see when you hop on the scales at home, you’re certainly not alone. Many of us rely on a combination of checking our appearance and our weight to measure weight change. Of course, if you’re serious about your fat loss or muscle gain goals, ‘losing weight’ is far too vague a target. You need a body composition test to help you formulate a clear plan.

What is a body composition test?

The most accurate way to measure your fat and lean muscle is through what is known as a Dexa body composition test. This scan uses a dose of ionising x-ray radiation and acts as a body fat calculator and a lean muscle calculator. Don’t worry, this radiation isn’t harmful at all and your body scan only takes around four minutes.

What measurements does it give?

Rather than just telling you how much your body weighs, your body scan report measures the lean muscle tissue, fat, and bone in your arms, legs, and torso. It also observes the amount of unseen fat that may have accumulated around your internal organs. 

Tracking progress

Your initial scan report gives you your starting point. You can have another scan as early as eight weeks to check your progress if you are observing a more intense fitness programme, but most have their next scan around 12 weeks to track changes.  

How we can help you

Though we specialise in dexa body fat measurement in the London area, we also offer a more basic body composition calculator, and we can help you determine your resting metabolic rate. From this, we can use our calorie calculator to determine exactly how many calories you need to maintain or lose weight.
Want to find out more? Read our customer reviews, or contact us for more information. We can’t wait to hear from you!

Celebrity magazines, newspapers and social media are forever blasting headlines about rapid weight-loss “miracles” achieved in just a few days. Many Bodyscan customers talk of their frustration when their weight changes day-to-day and is upward rather than downward.

Let’s get one thing straight. Your weight naturally fluctuates throughout the day and from day to day. And those short-term changes are not caused by increases or decreases in body fat. If your scales show you are a kilogram heavier than yesterday, you have not – repeat NOT – put on a a kilo of body fat! Significant changes in body fat take time (weeks and months) and occur as a result of a sustained net energy (calorie) surplus.

Short-term, daily body weight fluctuations are perfectly normal. Factors that can influence movement in body weight (independent of body fat) include:

  • Fluid balance (body water)
  • Salt intake
  • Muscle damage
  • Carbohydrate intake
  • Intestinal weight (food passing through your gut)
  • Stress
  • Menstrual cycle
  • Creatine supplementation (used by many bodybuilders)

In reality, changes in fat tissue are minimal or zero during a 24-hour period.

In simple terms, one pound (454g) of fat contains about 3,500 calories of energy. This is the premise behind the popular 500 calorie per day deficit dieting protocol, to lose one pound of body fat per week (seven days x 500 cals/day = 3500 calories = one pound of fat). [In metric terms, one kilogram of fat = 7,700 calories. Thus a kilo of fat loss per week requires a daily deficit of 1,100 calories.]

Based on the ‘3,500 calories per pound rule’, it would seem that if you eat 3,500 calories above maintenance you will store one pound of body fat in one day (at least in theory).

However, for a start, eating 3500 calories in excess of what you normally eat is quite some feat – it might mean eating two-and-a-half to three times your normal daily consumption.

Second, even if you could manage the sheer quantity of food, the additional 3,500 calories won’t necessarily lead to a gain of one pound of body fat. The reason is that when you eat big or very big meals, some of the energy from a large influx of calories in a short timeframe can be released as heat, which is not stored in the body. This is known as the thermic effect of feeding.

The response to overfeeding largely depends on genetics and lifestyle, and can vary significantly from person to person, even when over-fed by exactly the same number of calories.

So, unless someone has grossly overconsumed on calories (eg, 3,500-7,000 calories above maintenance), any jump in body weight over a 24-hour period is not even close to being all from body fat. In fact, the actual amount of fat stored will be relatively small.

Significant body fat is gained over weeks or months, not in hours or even days (for the most part). The marked differences in body weight after a short period of overeating are likely due to the fluctuation factors like body water, salt intake and food in the gut listed above.

However, persistent overeating will create a long-term, cumulative energy surplus over time, which will lead to body fat gain. If you eat 500 calories above maintenance every day for two months, that is 30,000 excess calories, some of which will get stored as fat, some as lean mass and some released as heat (as explained above). If you maintain the surplus (that is, regularly eat above maintenance), the total amount of body fat steadily increases over time.

​December (Christmas) is a month where many of us over-indulge on an almost daily basis, hence we hit New Year with an expanded waistline. But for many people, the holiday season just adds a spike to a smaller, but persistent, surplus of calories consumed every week between January and December and, with it, a slow but steady increase in weight and body fat over a much longer period of time.

While you shouldn’t take daily weight changes as evidence of changes in body fat, recording your weight at the same time every day will enable you to establish a longer-term trend. For best practice, record your body weight first thing in the morning, after the toilet and before consumption of any food or drink. If you take the average of your daily weight readings every seven days, THAT figure is a better one for understanding what is happening with body fat over the medium to long term.

Take other measurements too, such as progress photos and body tape measurements, and don’t rely solely on body weight. Or better yet, measure body composition with a DEXA body scan technology to obtain a detailed, accurate and consistent analysis of your progress.

Kevin Garde
Nutritionist and Bodyscan Consultant 

Healthcare experts are resoundingly clear when it comes to rapid weight loss. It is not only ineffective long term, but also places your body under observable stress leading to an array of health risks: ranging from decreased energy to more serious implications such as osteoporosis. The safest and most effective method of weight loss is to lose weight gradually over time.

How to lose weight gradually
If you’ve struggled to sustain steady weight loss, it may be time for a more targeted approach. A DEXA body composition scan is a form of body fat calculator that provides a fat mass index and a lean mass index. Essentially, this X-Ray scan gives you an overview of your body composition from which you can formulate specific fat loss or muscle gain targets. It also provides you with other key metrics for weight loss such as your daily calorie requirement as well as suggested calorie deficits that will help you to achieve your goals. Crucially, all of this information can be drawn upon to create an achievable and healthy framework specifically for your weight loss journey.

Creating a weight loss plan
For weight loss to be sustained over a long period, your nutritional and physical efforts need to be moulded around your existing lifestyle. At Bodyscan, we also offer a bespoke body transformation programme based on your DEXA body scanresults. Formulated with your food preferences and schedule in mind, we guide you throughout your transformation. We are by your side from the beginning and throughout your journey, with bespoke training and meal plans supported by regular check-ins and ongoing nutritional coaching.

We’ve delivered over 11,000 scans, and we’re really proud of the results our clients have achieved. If you would like to find out more about what we offer or how we can help you, please get in touch using our details here. We look forward to hearing from you!

What are high- and low-GI foods? Which are better, if any? What is the glycaemic index? Should I worry about it?
The glycaemic index (GI) is a food’s ability to raise blood glucose (sugar) levels.

Carbohydrates are ranked on a scale from 0 to 100 according to the extent to which they raise blood glucose levels after eating. In healthy people, protein has minimal effect on blood sugar and fat little, if any.

High GI carbs are those which are rapidly digested, absorbed and metabolised and result in marked fluctuations in blood glucose levels. Carbohydrates with a low GI (55 or less) are those that produce smaller fluctuations in blood glucose and insulin levels.

Let’s look at how the glycaemic index of food affects you in two ways:


At first blush, it might seem obvious that high-GI foods are unhealthy, as spikes in insulin and blood sugar are associated with heart disease and type-2 diabetes.

But actually, for overall health, the GI of dietary carbohydrates have little if any meaningful impact if your diet is ‘sensible’ and consists predominantly of whole foods and minimal highly refined junk-type foods.

While current evidence shows modest beneficial effects of a lower-GI diet compared to a higher-GI diet in terms of glycaemic control and blood lipid profile, it’s important to note that comparisons of different-GI diets often fail to take account of macronutrient and fibre content. Lower-GI foods and diets often have a ‘head start’ because they are typically higher in fibre, protein and micronutrient density.

Body Fat

It is often claimed that high-GI foods lead to an increase in hunger and therefore body fat, partly due to the stimulatory effects of insulin. But contrary to popular belief, insulin has actually been shown to suppress appetite. A classic example of the misconception around high-GI foods and appetite response is boiled potatoes, which have been shown to be highly satiating (meaning they make us feel full).

Another finding that contradicts the widely held belief that only carbs spike insulin: protein-rich beef has been shown to be as potent a stimulator of insulin as carb-heavy brown rice, even though protein raises blood glucose to a much smaller extent than carbs.

It’s also important to note that the GI response of a given food differs between individuals and can be affected by what it’s eaten with (e.g. alongside protein, dietary fat and fibrous veg). As such, worrying about the GI of one food in isolation holds little relevance in most real-world scenarios where there is more than just one ingredient on your plate.

Studies have consistently reported that once confounding variables (e.g. fibre, energy density and macronutrient content) are controlled, neither dietary carbohydrate nor GI has an effect on body composition and on overall energy intake.

Take-home message:

For fat loss, eat in a way that leads to the greatest adherence towards an appropriate energy deficit over time. Poring over GI indices is, frankly, a poor use of time and energy! Instead, create a diet with ample protein, fibre and one that is rich in micronutrient density.

For overall health, think more about the nutritional quality of a given food rather than worrying about its rank on the GI scale. A variety of nutrient-dense foods is considered ‘the spice of life’.

Kevin Garde
Nutritionist and Bodyscan Consultant