Factors Affecting the Scale

The scales can be a bit of a battleground for a lot of people. Most would agree that true weight gain or loss can be determined by both how clothes fit and what you see in the mirror. Despite this, if we jump on the bathroom scales and see a number that doesn’t align with our effort or what we see in the mirror, it can send some people into a spiral.   

Though we are aware of weight gain that can occur in the luteal phase, with an increase in water retention and digestive changes, several other factors will also affect the scale number on any given day. Regardless of how you feel about them, scales are truthfully a good assessment of the trend in your body weight over several months. But all the in-between values can go up and down depending on a range of acute factors, which are outlined below.  

Carbohydrate intake: we store dietary carbohydrate predominantly in our muscles as glycogen - which is awesome, as it is then available for use the next time we exercise. For people who generally eat lower carbohydrate, their glycogen stores will likely be lower than someone who follows a higher carbohydrate diet. This is also true for people who are in a fat loss phase and overall have a lower absolute number of calories. For these people, then, it is likely that a higher carbohydrate meal will result in a heavier number on the scale. For every 1g of carbohydrate you store, you store an additional 3-4g of water. This is why, after a higher carbohydrate meal or day, the scales can go up by at least 1-2 pounds, more if you are a lucky individual who carries a lot of muscle.

Sodium: if you had a meal that was high in salt (which is made up of the two minerals, sodium and chloride) then you will undoubtedly weigh more the next morning. This is because sodium pulls water into the cells, so even in the absence of carbohydrate your body will be holding more water. A sushi meal out, salted popcorn, cured meats or a restaurant meal that is often higher in sodium will all likely result in a heavier weigh in the next morning.  

Fiber: a diet higher in fiber will make you feel more satisfied, can assist adherence to a calorie deficit and help you lose body fat. However, a meal that is high in fiber can result in a heavier weigh in.  Fiber adds bulk, and if it hasn't had time to move through your digestive tract, then you can see the impact of that on the scale. Soluble fiber adds bulk to your stool, whereas insoluble fiber acts like a broom, and sweeps through your digestive tract to speed the transit of material through your bowel. Both types of fibers are present in most foods, though if you have more soluble then it's likely that you'll notice it more. In addition, those people who experience gastrointestinal issues that include bloating and constipation are not going to get an accurate reflection of fat loss progress based on body weight (this might go without saying).

Inflammation: if you weigh yourself the day after a hard/long workout, then your muscle fibers may well still be recovering, and be experiencing some level of inflammation. The microtrauma to the muscle fibers cause the fibers to retain water, and you'll see that on the scales. This is often deflating for an athlete who is both training hard and shooting for a body composition change. It can take a few days for the weight change to settle.

Meal timing: if you eat later than normal, there isn’t enough time for the bulk to move through your digestive system.

Poor sleep: a disrupted sleep can elevate our cortisol levels, and this impacts your sodium and potassium levels. This change can lead to an increase in water retention and subsequent increase in the scales. 

Stress: Most people recognize how stress in the long term can result in changes in food behavior along with a change in how the body stores nutrients. In the short term, an overstressed system can temporarily lead to a heavier weigh in. It was mentioned above the change in water retention that occurs in the acute sense after a poor nights’ sleep with regards to cortisol. In addition, high stress that elevates cortisol can slow gut motility, and impact scale weight. 

Miscellaneous reasons for scale fluctuations include environmental factors such as temperature and humidity, with the humid environment reducing the ability to lose heat through sweating, and the increased cortisol response to heat stress both affecting water balance. Some medications such as anti-inflammatory medications can cause an increase in extracellular fluid and affect scale weight.

Does this mean that you shouldn't weigh yourself on days you know will be higher due to some of the reasons outlined above? No. I think it can be a good exercise to observe how this changes day to day so you can get comfortable with the numbers and remove the emotional attachment to the number. It is just data.  You can see a trend over time (i.e. if your weight is tracking up or down) regardless of this day-to-day fluctuation. Of course, the most important things to track are your adherence to your diet, how you feel, how you look and how you perform. In time, the scales will reflect this effort.

References 

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