The Limitations of Common Ways of Determining Weight Loss

People who are eating differently in an effort to lose weight often hop on the scale daily to see how they’re doing. What they fail to consider is that an average adult’s body weight can fluctuate by as much as 4  1/2 pounds per day — solely as a result of changes in the amount of water they are retaining or excreting.

The Limitations of Using a Scale to Determine Fat Loss

An 80 kg person has, on average 48 liters of water in their body. The problem with using body weight as an assessor of fat loss is that the human body does not precisely regulate body water content.

Above 49 liters of water, the kidneys of an 80 kg person will clear the excess water by causing the person to urinate more and below 47 liters of water, the 80 kg person will feel thirsty and increase their fluid intake. People’s “weight” is affected by this change in body water content of ~2 liters per day — which weighs approximately 2 kg or 4.4 pounds! Put another way, each day our “weight” can fluctuate by this amount solely due to the difference in retained or excreted water.

Since there is no way to measure this daily change in water weight in non-clinical settings, the standard scale is a very imprecise way to measure fat loss over the short-term.

Waist Circumference

Many people know that carrying excess weight around the middle increases one’s risk of cardiovascular disease, including heart attack so they measure their waist circumference frequently. Even if waist circumference is measured halfway between the lower rib and the top of the hip bone, with a fully relaxed abdomen, their are limitations to using this as a short term measure of weight loss.

The Limitations of Using a Tape Measure to Determine Fat Loss

Since the average person’s body weight fluctuates by as much as ~4 1/2 pounds per day due only to changes in body water, a tape measure fails to capture decreases in waist circumference stemming from the kidneys excreting water.

That said, waist circumference is helpful as a long-term indicator of weight loss, just not a short-term one.

Body Fat Percent

Some people have bathroom scales that have body fat analyzers built in and think that what it is measuring is the amount of fat they are carrying, however a number of factors can influence this reading.

The Limitations of Using a Body Fat Analyzer to Determine Fat Loss

Body Fat Analyzers use electrical impedance to determine fat percentage, and this measurement is affected by a number of conditions, including environmental (room) temperature, a person’s hydration status, as well as emotional stress. Since hydration status can fluctuate by ~4 pounds per day, a body fat analyzer is no more accurate as a short-term measure than a standard bathroom scale, without it.

How to assess short-term weight loss

How one’s own clothes fit and comparative ‘before’ and ‘after’ photos are a much better short-term assessor of fat loss than a scale, a tape measure and a body fat analyzer. Since body water fluctuates considerably on a low carb high fat diet due to changes in sodium levels, I recommend that people eating a low carb high fat diet weigh themselves once every two weeks on the same day of the week, at the same time of day and measure their waist circumference at the same time. If they have a scale that assesses body fat percent once every two weeks is sufficient for taking these measurements.

None of these will provide much information on actual fat loss over the short term…so why rely on them for that, but they will be helpful measurement over the longer term.

Sodium and Body Water Content

As mentioned in a previous article, by eating only when hungry and only until no longer hungry, insulin levels have the opportunity to fall to baseline – something they do naturally after not eating for 12 hours.

On days where the time until eating is extended by a few hours (i.e. “intermittent fasting”), insulin levels stay low for an even longer period of time.  In response, our kidneys excrete sodium in a process called naturesis.

Failing to supplement sodium while eating low-carb high fat can result in intense headaches – and if sodium remains low, potassium will also be excreted to keep the necessary sodium-potassium balance. This drop in potassium often results in irregular heart beats, known as arrhythmia.

Phinney and Volek (The Art and Science of Low Carbohydrate Living) recommend that if one is eating less than 60 gms of carbs per day, that 2-3 grams of sodium should be added to the diet (provided the person is not taking any diuretics or other blood pressure medication).

A half a teaspoon of table salt or sea salt provides 1000 mg or 1 gram of sodium.

Final Thoughts

Since hopping on the scale daily or even several times a week won’t provide any useful information, nor will measuring our waist circumference or using a body fat analyzer too often – why do it? Part of ‘getting healthy’ ought to include having a healthy body self image – something that won’t be nurtured by obsessing about such “numbers”.

Short-term measures of success

Short-term success is best measured visually – with comparative photos taken from the same distance away, from the same relative height and wearing the same clothing.

How one’s clothes are fitting is another way.

A person who is insulin resistant or Type 2 Diabetic should be seeing both their fasting blood glucose and post-prandial (2 hours after a meal) glucose levels gradually coming down. If they aren’t then they should schedule an appointment with their Dietitian to find out why that is.

Medium-term measures of success

Medium-term measures of success in eating low carb high fat can be measured both subjectively and objectively. Subjective measures include weighing oneself and taking one’s own waist circumference once every two weeks. Objective measures include having your Dietitian weigh you on a clinical scale, having her assess your waist circumference and body fat percentage using both a device that measures electrical impedance, as well as using good old-fashioned calipers, that measure subcutaneous (under the skin) fat, in 3 or four specific locations on the body.

A person with high blood pressure should be seeing both systolic (the first number) and diastolic (the second number) blood pressure coming down and Type 2 Diabetics or those with insulin resistance should be continuing to observe lower fasting blood glucose and post-prandial (2 hours after a meal) glucose levels.

Longer-term measures of success

After 6 or 8 months eating low carb high fat, both subjective and objective measures should be continuing to lower in a reasonably linear fashion. Of course there will be times where a ‘plateau’ is reached, but if that lasts more than two or three weeks, then its important to check in with your Dietitian to make sure the amount of carbs you think you are eating is what your Dietitian has been determined as being best for you.

A Type 2 Diabetic should be seeing both their fasting blood glucose and post-prandial (2 hours after a meal) glucose levels approaching more normal levels and both Type 2 Diabetics and those with insulin resistance (“pre-diabetes”) should have their HbA1C assessed at a lab every three months, as this provides insights into one’s 3-month average blood glucose level. Fasting blood glucose provides a ‘snap-shot’ of blood sugar in the morning after not eating, and should be done twice a year by a lab, especially if one is Diabetic. Comparing lab test results to previous lab test results is an objective indicator of the effect that eating low-carb high fat is having on specific markers and provides an opportunity to determine if the amount of carbs being eaten may still be too high.

The most accurate assessor is a 2 hour glucose tolerance test, however few doctors will requisition this after one is diagnosed as Type 2 Diabetic.

Finally, every year or so, it is helpful for those who have been diagnosed as Diabetic to have their fasting insulin, C-Protein and AM Cortisol levels assessed and compared to previous results. For these, your doctor may refer you to an Endocrinologist.

Remember, achieving health is a journey and takes time and like most journeys, it is best not done alone.

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To your good health!

Joy

Note: Everyone’s results following a LCHF lifestyle will differ as there is no one-size-fits-all approach and everybody’s nutritional needs and health status is different. If you want to adopt this kind of lifestyle, please discuss it with your doctor, first.

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