The Scale Paradox: A Comprehensive Guide on Using Bodyweight Data

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This is a guest post by Kevin Garde. For more info about Kevin, see the section below this article.


When it comes to the world of health and fitness, it is hard for many people to escape the notion that the number we see on a body weight scale provides the most important data point to being healthier and happier. And there is no shortage of conflicting views and controversy when it comes to opinions on the usefulness of scale weight.

On an individual level, it often evokes a sense of negativity; as the displayed number leaves many both disheartened and demotivated. In other cases the data is encouraging; a welcome stimulus to embark on a weight loss journey.

To start, I would like to preface this article by making a critical and important distinction: what the scale does measure vs. what it does not measure.

What the scale DOES measure:

  • Total body mass.

What the scale DOES NOT measure:

  • Body composition (fat mass vs. lean body mass)
  • Self-worth
  • Competence
  • Personality

Yet for so many, these intangible qualities are intertwined and dependent on some arbitrary number appearing on the scale. This is unfortunate, and can lead to a whole set of ill-informed ideas and notions, which may promote irrational behaviours. All too rarely does the scale number invoke the sense of positivity and motivation to carry on, along a steady, progressive path, or, to make adjustments, if it is not leading to the goal in mind.

This is a crucially important message that practitioners need to remind themselves of (and their clients too), from time to time, and indeed all readers should note.

It is not unusual to find that mixed feelings associated with the body weight scale are heightened among dieters, especially among those who experience a sudden body weight fluctuation, often in the ‘wrong’ direction, or, worse, the dreaded weight-loss plateau. Typically, I find the missing piece for many is simply a lack of understanding why body weight fluctuations might occur. Couple this with an uncertainty regarding how much fat tissue gain is realistically possible on a day-to-day basis and one can begin to understand where the confusion lies.

The scale is all well-and-good as one (of the many) methods to monitor progress, but a single data point shouldn’t be held to the importance people often place on it. For someone aiming to lose body fat, just because the number on the scale is up compared to yesterday’s value, it doesn’t necessarily mean the person had had a ‘bad’ day, nor does it mean that their diet ‘isn’t working’.

Before we delve into the nuances governing body weight fluctuation, and the potential benefits and/or pitfalls in using the scale as a tool to monitor progress, it is important to acknowledge that daily weighing may not suit everyone, and its usefulness needs to be assessed on an individual basis.

Whatever your body composition goal, it is recommended to track some form of objective metric (and subjective metric) to assess progress. This enables you to regularly accomplish ‘easy wins’ – a motivational strategy particularly pertinent to those with significant body fat to lose, or those who may need major behavioural and lifestyle modifications to achieve goals.

Changing Body Tissue Mass: How to Use the Scale Effectively

A change in body tissue mass is most closely related to energy balance over time. Thus, the fundamental principle for meaningful fat loss to occur is adherence to an appropriate and sustained energy (calorie) deficit. This can be achieved via calorie restriction through the diet, an increase in energy expenditure, or a combination of both.

As many readers will be aware, the body weight scale cannot differentiate between different bodily compartments (e.g. lean body mass, muscle tissue, fluid balance, bone density, fat tissue, etc.) and therefore cannot determine your body composition (that even includes that fancy scale that claims it can provide an accurate body fat reading – it doesn’t!).

With this knowledge, people have to be aware of what the scale actually tells us. In other words, context matters. For example, an increase in body weight does not necessarily mean an increase in fat tissue. Despite this many people have been conditioned to assume that a drop in body weight always means fat loss and an increase in body weight must always mean fat gain. This is simply not the case.

Scale weight is susceptible to short-term fluctuations. All too frequently, a sudden jump in body weight disheartens people, with many deciding to forego the merits of the body weight scale as a fat loss tool. Ironically though, with the correct education and support, an individual self-weighing, near daily, will learn to differentiate the ‘noise’ of day-to-day body weight fluctuations from the underlying trend.

A similar scenario arises with body weight plateaus. A fresh perspective on body weight plateaus, highlighted by Alan Aragon, suggests that instead of viewing plateaus as failure and frustration, a simple shift in mindset to embrace this period as practice for weight loss maintenance (a far more difficult endeavour than weight loss itself) may alleviate some of the stress typically associated with body weight plateaus, and set the correct mind-frame for a further fat loss phase (goal-dependent, of course).

Before outlining a suitable method to track body weight, it is of key importance to educate clients on the nuances of body weight fluctuation, alerting them to the possible causes behind perceived increases, or decreases, in body weight. For example, forewarning clients that a rapid fall in body weight may occur during the initial phases of a fat loss program, and not all of this will be body fat loss, e.g. manipulating carbohydrate intake can have a huge impact on scale weight. Keeping clients informed from the outset can help build rapport and ‘buy-in’, qualities that are invaluable throughout the coaching process, and which strengthen adherence.

As mentioned previously, many dieters are often disheartened when the scale does not indicate a reduction in body weight on a day-to-day basis, despite one’s best efforts, e.g. strictly adhering to a dieting protocol and consistently partaking in physical activity/exercise. Experienced dieters, however, are more accustomed to daily fluctuations, and are aware that body weight loss is seldom linear and can unexpectedly fluctuate from one day to the next.

Nuances Associated With Body Weight Fluctuation

Acute, short-term, daily weight fluctuations (gains and losses) are perfectly normal and can happen for a number of reasons. Outlined below are some of the factors that can influence body weight fluctuation, independent of body fat gained or lost:

#1: Fluid Balance – dehydration will cause weight loss as there is less fluid within the body. 1L of fluid equates to approximately 1kg of body weight. Water loading/restriction strategies among weight-making athletes have recently been shown to be an effective method to reduce body weight acutely under certain conditions. But there is no change in fat tissue here. It’s just dehydration. Outside of the weight-making performance realm, an individual may notice a drop in measured weight, for example, after a period of binge alcohol consumption or excessive sweating – this is not indicative of actual fat loss, but a measure of the weight of fluid lost to dehydration.

#2: Salt Intake – salt stimulates thirst and therefore may cause a person to drink more, leading to acute weight gain. Salt also causes water to be retained within the body, i.e. it is a powerful agent in rehydrating. Therefore, if a person eats a particularly salty meal, the body is more likely to store water which could lead to acute weight gain. So again, there is no change in fat or muscle tissue but there is an increase in body weight. This is temporary phenomenon, and will be reversed after a couple of days of solid dietary adherence.

#3: Muscle Damage – muscle damage from weight training and exercise can cause muscular inflammation and associated water retention. The subsequent increase in body water can result in acute weight gain.

#4: Carbohydrate Intake – with every 1g of carbohydrate stored inside the body (as glycogen), an additional ~3g of water is stored. The two major sites of glycogen storage are the liver and skeletal muscles and can account for approximately 5-10% of the weight of the liver and 2% of skeletal muscle weight. Note – more total glycogen is stored in skeletal muscle due to its much greater total mass.

If, for example, 400g additional carbohydrates are stored within your muscles, an extra 1.2kg water will also be stored. This equates to 1.6kg of acute total body weight gain. Taking into account that our bodies can store between ~400-800g carbohydrate within muscle tissue, and ~80-100g in the liver, it is easy to see how consumption of a high carbohydrate meal could have an effect on body weight.

Similarly, if an individual embarks on a lower carbohydrate diet, the subsequent drop in glycogen stores (and associated water) will lead to a reduction in total body weight. This strategy can be used to great effect to achieve initial client buy-in, and is a frequent feature among many popular low-carbohydrate dieting protocols as rapid weight loss typically ensues within the first week or so of the diet. It is important to reiterate that the magnitude of the energy deficit alone will determine the rate of body fat loss, and not the ratio of carbohydrates to fat – a detail often ignored by low-carbohydrate zealots/advocates who believe that carbohydrates are uniquely fattening, due to the effects of insulin.

As depicted by the graph below (a client’s body weight over a two week period – under dieting conditions), acute, short-term, daily body weight fluctuations (gains and losses) are completely normal, while the overall trend shows a net weight loss over the period.

#5: Intestinal Weight – eating a high volume of food (e.g. having a treat meal, while following a calorie deficit routine), increases the volume of food in the intestines causing acute weight gain, or, at least, masking fat-related weight loss.

Similarly, bowel movements, which can vary greatly among individuals, impact scale weight. Greater food volume and fibre intake can play significant roles here. Urine output is another variability factor and is dependent on hydration status. It is for these reasons that standardising the daily self-weighing protocol (i.e. first thing every morning, post-void) is recommended when monitoring progress.

#6: Stress – chronic stress can cause changes in certain hormones such as cortisol. Cortisol crossreacts with the aldosterone receptor (involved in regulating fluid balance) and therefore may influence body weight through its effect on water retention, leading either to weight gain, or weight maintenance, despite hypocaloric (dieting) conditions. Extreme examples include Cushings disease, where cortisol production is out of control and can cause huge levels of water retention.

As an example, during an established starvation study on obese men and women, wide individual variations were most apparent in females throughout the latter weight loss phase – the differences are thought to be due to variable, but reversible, water retention by the kidneys.

Another condition associated with variations in the levels of urinary cortisol excretion is cognitive dietary restraint – restraint is the conscious restriction of food intake to prevent weight gain or promote weight loss. One study, assessing 24-h urinary cortisol excretion differences between women with high and low restraint scores found that there was a 15% increase in basal cortisol levels in the high restraint group compared to the low restraint group. Over time, this may lead to cortisol-mediated water retention and thus mask fat loss progress, if using the body weight scale alone.

#7: Menstrual Cycle – women’s weight and body composition is significantly influenced by the female sex-steroid hormones. Levels of these hormones fluctuate dramatically throughout the menstrual cycle and, during certain time periods, it is not unusual for women to experience anywhere between one to ten pounds (~0.45kg-4.54kg) of weight gain. For those women who are susceptible to large water fluctuations during a regular cycle, it may be prudent to compare body weight rolling averages month-to-month.

#8: Creatine Supplementation – creatine, one of the most well-researched and effective supplements on the market can cause notable increases in body total body water of 6.2% over 4 weeks and 1.1kg over 42 days, following an acute loading phase and a typical maintenance dose of ~5g daily. Lower doses may cause less water retention.

Realistic Changes in Fat Tissue Over a 24-Hour Period

Alongside equipping clients with knowledge surrounding the nuances associated with body weight fluctuation, education regarding realistic, day-to-day increases in fat tissue is also crucial. In truth, changes in fat tissue are minimal during a 24-hour period (in most realistic scenarios).

For those who may not be aware, a pound (454g) of fat contains ∼3,500 calories of energy (if interested in where that value stems from, read this). This is the premise behind the popularised 500 calorie per day deficit dieting protocol, to lose one pound of body fat per week.

Based on the ‘3,500 calories per pound rule’, it would seem you would need to eat 3,500 calories (kcal) above maintenance to store one pound of body fat in one day (at least in theory). Eating 3,500 kcal above baseline, however, won’t necessarily lead to a gain of one pound of fat. The reason is that some of the energy value of a large influx of calories in a short time period can be released as heat, which is not stored in the body.

[The science: An increase in the thermic effect of feeding (due to a larger volume of food), coupled with the possibility of replenishing glycogen stores and up-regulation of non-exercise activity thermogenesis (NEAT), can attenuate the ‘predicted’ amount of fat gained. Note – originally NEAT represented unconscious movements/activity such as fidgeting. More recently, NEAT encompasses all activity outside of formal exercise, including grocery shopping, step counts, flights of stairs etc].

The response to overfeeding largely depends on genetics and lifestyle, and can vary significantly from individual to individual. This is true even where people are over-fed by exactly the same number of calories, NEAT (non-exercise activity thermogenesis) can account for a ten-fold difference in body fat accumulation.

So, unless someone has grossly overconsumed on calories (e.g. 3,500 – 7,000 kcal above maintenance), that 0.5-1 kg (~1-2 lb) jump in measured 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. Nonetheless, individuals are still less likely to weigh themselves the day after an excessive feed.

Briefly touching on the topic of overindulgence, how you or your client responds following an episode of excessive eating is what really counts for long-term weight management! The best approach is to move on and get back ‘on it’ the next day. Remove the notion that you must starve yourself, or seek punishment with copious amounts of cardio to compensate, as this will likely promote unhealthy behaviours. Instead, get back on track the following day and continue to build healthy habits that support your goals.

Significant body fat is gained over weeks or months, not in hours or even in days (for the most part). The marked differences in body weight after a short period of overeating are likely due to the factors surrounding body weight fluctuation touched on earlier, such as carbohydrate and salt intake, exercise and intestinal weight.

Does the data support the use of the body weight scale for weight loss?

A systematic review by Ramage and colleagues found that the following criteria were critical components for significant, safe weight loss and weight loss maintenance: an energy deficit, regular physical activity, and behaviour strategies, including self-monitoring and educational programs.

Daily self-weighing is a self-monitoring strategy that has shown promise for weight loss and weight loss maintenance in overweight and obese individuals. This supports the theory that individuals are better able to self-regulate behaviours when they self-monitor and evaluate current behaviour, compared to goals. That is, behaviour change begins with awareness of a problem, and a personal decision to amend habits accordingly. One study reported that 44% of individuals who maintained a significant weight loss for at least one year self-weighed daily.

Not only can regular weighing improve weight loss results but it is also possible that daily self-weighing may be important for prevention of unwanted weight gain. Daily self-weighing has helped college freshman women prevent weight gain over 12-weeks and have better weight maintenance over a year-long intervention, compared to a control group.

In a study published in 2017, Rosenbaum and colleagues found that daily self-weighing was associated with significant declines in body mass index (BMI) and body fat percentage over two years in college-aged women. This study was unique in that it investigated the relationship between daily self-weighing and body fat changes over time. The authors concluded that “daily self-weighing may be important not just for weight maintenance among those with prior weight loss histories, but also for initial prevention of unwanted weight gain.” This is consistent with obesity literature that found more frequent self-weighing is associated with greater weight loss, and weight gain prevention.

Although the literature examining daily self-weighing outside of obesity is limited, there are some reports that suggest this behaviour may be beneficial for weight gain prevention in young adults. In young adults, regular self-weighing is associated with greater use of healthful weight control management, and greater weight loss over time, among those seeking to lose weight, or prevent weight gain.

The majority of the aforementioned studies are correlational in nature and, given that daily self-weighing does not influence weight loss directly (but rather via a sustained energy deficit, physical activity and lifestyle behaviours), it is important to begin to acknowledge the changes in behaviour triggered by daily self-weighing itself.

A more recent, 6-month, randomised, controlled trial sought to determine whether daily weighing is associated with greater adoption of weight control behaviours compared to less frequent weighing. This study provided a unique opportunity to assess the efficacy of daily weighing during weight loss interventions using an e-scale to obtain an objective measure of self-weighing frequency.

Results showed that daily weighers lost significantly more body weight (~6.1kg more total body weight on average) compared to those weighing less frequently (note: body fat loss was not measured). It was also found that daily weighers were more likely to implement behaviours related to weight loss, such as eating less fast-food or watching less television.

Interestingly, both the aforementioned study and an earlier study by the same group included weekly email correspondence with tailored feedback and lessons; daily self-weighing participants reported positive weight control behaviours. All in all, it appears that the weight loss benefits of daily weighing are strengthened when coupled with continued education, knowledge and an on-going social support/feedback system in place.

Arguments against the use of frequent self-weighing have also been noted within the literature, with the primary concern being that it can be psychologically harmful for certain individuals. Of interest, the impact on body dissatisfaction and the resulting disordered eating behaviours (e.g. purging, fasting) may surface when individuals are asked to bring their attention to their weight on a daily basis, particularly if it falls outside of the ‘normal’ or ‘expected’ range. In today’s society, this links back to the issue where some individuals are prone to tie self-worth to an arbitrary number on the scale. Even though some degree of dissatisfaction can provide a positive stimulus for change, there is reason for caution about the potential exacerbation of body image concerns via weight monitoring.

With that in mind, practitioners/nutritionists/personal trainers need to be aware of the potential adverse psychological outcomes associated with daily body weighing for certain individuals (such as those with a history of disordered eating and/or lowered self-esteem). Caution is also advised with female adolescents who may be particularly vulnerable to disordered eating behaviours in association with frequent self-weighing. In contrast, with male adolescents it appears that self-weighing does not give rise to unhealthy weight control behaviours (at least to the same extent).

Another potential consideration is that the initial positive healthful behaviours associated with daily self-weighing may become diminished over time, akin to many fresh, exciting lifestyle modifications (at least from the onset) such as calorie tracking, sleep tracking, or step counting. In many cases, adherence eventually plummets and healthy habits may even be viewed in a negative light. This has been seen with frequent self-weighing too, which showed a decline in adherence to self-weighing over time.

With twenty studies available to date on associations between self-weighing and negative psychological outcomes and/or weight control behaviours (the majority of which are observational), conclusions appear to be equivocal, and therefore variability among individuals may be high.

As such, it is up to the practitioner, or the individual, to determine whether frequent self-weighing is deemed a suitable approach to monitor progress, both from a fat loss and muscle gain perspective. If deemed unsuitable, it may be prudent to consider alternative means to obtain objective data. Another, and perhaps a more appropriate, option could be to adopt performance-based goals, an approach highlighted and discussed in this Sigma Nutrition episode with Mike T. Nelson.

To Weigh or Not To Weigh?

Daily weighing isn’t suitable for everyone in all scenarios. For some, it will spur them on to continuing healthful behaviours and develop habits in line with their goals. For others, it may stimulate a negative feedback loop and encourage unhealthful behaviours associated with body dissatisfaction and may even promote a poor relationship with food. The best approach is to trial self-weighing for yourself, or your clients, for a number of weeks and assess accordingly. We know that it can be surprisingly difficult to notice weight gain creep up over time, particularly when the focus is on other aspects of one’s life.

Where applicable, a pragmatic approach, that practitioners/nutritionists/personal trainers can provide, may be to foster a level of weight-related concern that serves to motivate rather than demoralise. Many clients respond well to the challenge presented by weekly tracking/targets to accomplish easy-wins, as it can motivate and reinforce effective behaviour change. When it comes to physique aspirations (particularly for leaner individuals), it is important to encourage striving for a desired look rather than an arbitrary number on the scale.

I firmly believe that, as with any intervention, it is important to follow up with the individual/client to ensure that self-monitoring methods are utilised as useful tools and not promoting harmful effects on mood, attitudes, or behaviours. If the latter is the case, individual issues need to be addressed from the onset and coached accordingly.

Tracking and consistency

If an individual decides to adopt self-weighing as a tool, the best practice is to weigh oneself first thing each morning, post-void (with minimal clothing and before consumption of any food/drink) and assess progress on weekly or bi-weekly rolling averages. Consistency here is key, as faecal weight and urinary output can have significant impacts on day-to-day weight variation. If fat loss is the goal, one should typically see a downward trend over time.

How much self-weighing is too much?

Again, this depends on the individual but aim to be consistent. When tracking progress over a given period, it is best to avoid taking isolated body weight measurements, e.g. once per week/fortnight. The rationale being, that body weight, when taken in isolation, does not take into account normal, day-to-day body fluctuations. If an individual were to use the previous two-week body weight trend, as outlined before, on the first day of each week (i.e. day 1, day 8 and day 15) – that individual may start to question the nutritional fat loss approach, based on body weight readings alone (i.e. 87.2 kg, 86.2 kg and 86.7 kg, respectively).

This can become even more apparent when comparing alternate weeks of a regular female cycle. By taking body weight measurements daily, and looking towards a weekly or fortnightly average, it is easier to differentiate the ‘noise’ of day-to-day body weight fluctuations from the underlying trend.

Remember, daily body-weighing is one method to assess progress. Ideally, supplementary, objective metrics should be recorded too, such as progress photos and body tape measurements, and not rely solely on body weight alone. Again, being consistent here is key, i.e. similar lighting, time of day, same tape, etc. The frequency I typically request is every four weeks for photos, and two to four weeks for tape measurements. Better still, record skinfold measurements every couple of months by a qualified anthropometrist to obtain a clearer picture of body composition progress. For a more detailed insight into how to track client data correctly, check out this fantastic article by coach Andy Morgan.

By including a variety of different methods to track progress, an individual can detect subtle body composition changes while no major changes may be detected on the scale, e.g. body recomposition (the simultaneous loss of fat, and gain in muscle mass). A typical body recomposition scenario could be an individual, new to training, or experiencing a novel training stimulus, showing a decrease in waist circumference while scale weight remains unchanged.

Take-home Message

Be sure to use a number of complementary methods to assess body composition progress, and understand the nuances associated with body weight fluctuation. Be mindful, without being obsessive, of minor, normal, day-to-day fluctuations, and do not worry about a sudden drop, or gain, in body weight over a 24-hour period. A short-term gain is most likely a combination of water, glycogen and intestinal weight factors, and only a small fraction of body fat (if in an energy surplus).

Aside from its usefulness as a gauge to estimate progress, daily self-weighing can also provide accountability, motivation and spur individuals into pursuing more healthful activities, related to weight loss and/or weight maintenance, at the start of each day. Most importantly, however, through knowledge and education, clients also know not to be disheartened by a minor jump in body weight (either way!) from one day to the next. Be patient, and trust and embrace the process – as Sohee Lee eloquently stated ‘Be proactive, not reactive, about scale weight… context matters’.

About The Author

Kevin Garde is a Nutrition Consultant specialising in fat loss, body composition, sporting performance and is the founder of PRISM Nutrition. He has a Master’s Degree in Sport and Exercise Nutrition from Loughborough University, and previously worked as a nutrition consultant at Mac-Nutrition. Kevin is a member of the Sport and Exercise Nutrition Register, the British Dietetics Association, and is an ISAK accredited anthropometrist. You can find him on Instagram at @kevgarde_prismnutrition or via his website HERE.

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