It takes practice and experience to be able to look at weight objectively. It’s easy to throw in the towel when, despite your best efforts, the scale shows that you’re up by 0.5kg from the previous day.
While it’s definitely a good idea to check weight more than just once per week if it’s something that you’re monitoring, if you struggle with the psychological aspect of the ups and downs, it may be because you don’t fully understand the erratic nature of bodyweight. Let’s delve into some of the factors that influence scale weight and how to account for them.
Carbohydrates
For every gram of carbohydrate we eat, each is capable of holding onto 3g of water. It’s quite common to restrict calories through carbohydrates when dieting for fat loss, as it is to place re-feed days at times for either psychological or physiological benefits. In both cases, bodyweight can be affected quite significantly.
When reducing carbs, our bodies will hold onto less water. When increasing carbs, our bodies hold onto more water. Changes in bodyweight from one day to the next, can in part be attributed to changes in body fat and (to a smaller degree) lean muscle mass, but when you experience a kilo swing in either direction, it’s a safe bet that it’s mostly down to changes in fluid retention.
You can hopefully start to see how this might be a problem in the context of fat loss, as most people tend to check weight each Monday morning first thing after a weekend. All week you’ve followed your diet, stuck to a deficit, trained, hit your steps and sleep, etc. and then Sunday evening was a meal out (very heavy on salt, more on this later) that added an additional 50g of carbs to your daily intake. It’s not unusual the next morning for the scale to show that you’re heavier than a week ago, which starts off the self-sabotaging behaviour that so many people have on a semi-permanent loop.
However, if you had taken a daily weigh-in, the results might have been quite different, and given you peace of mind. Below is an example of how both scenarios might look.
Person A
Checks weight on Monday: 80kg
Follows the plan to a T until Sunday night, then goes for a burger but is still within calories, but goes higher on carbs and sodium for the day.
Monday morning weight: 80.7kg
Resulting mindset: must have gained fat, burgers make you gain weight, never eat burgers again, start eating cauliflower rice instead of carbs, become a grump, hate life, crash your car, lose your job,…that escalated quickly.
Person B
Checks weight 7 days per week and follows the plan to a T until Sunday night, then goes for a burger but is still within calories, but goes higher on carbs and sodium for the day.
Scale weight
Monday: 80
Tuesday: 79.8
Wednesday: 79.6
Thursday: 79.6
Friday: 79.4
Saturday: 79.3
Sunday: 79.1
Monday: 80.7
Average weight for that week (excluding the 2nd Monday): 79.5
Resulting mindset: understands that they will start the new week slightly heavier but the weight will likely come down quite fast once the body flushes everything out, goes right back to the plan, sees improvements in measurements, and ends up at a new low weight by the end of the following week.
Sodium
We briefly touched sodium (salt) and how it can also skew bodyweight. Amongst other electrolytes, sodium is involved in regulating the body’s fluid balance.
When we eat very salty foods, the concentration of sodium in our blood exceeds the homeostatic or balanced level that our bodies like to maintain, and our brain interprets this as dehydration or thirst. We drink water to raise the amount of water in our blood so that it dilutes the sodium levels back to normal ranges. If you jump on the scale after drinking a litre of water following a salty meal, you'll be up by a kilo, as well as by whatever the food you ate weighed.
Conversely, when we don’t eat enough salt, our bodies also interpret this as dehydration. The sodium levels in our bloodstream are now too low, so our bodies will try to balance this out by getting rid of more fluid, which is why we tend to go to the toilet more to pee.
Eating very salty meals means that we tend to hold onto more water both through sodium binding onto water molecules, as well as through the fact that we’ll feel the need to drink more water to balance the higher levels in our bodies. If we’re low on sodium, not drinking enough water, and urinating frequently, we’ll be holding less water, which means that we will for all intents and purposes be lighter. Not holding onto less body fat, simply lighter.
Digestive Health
Regularity in bowel movements should be strived for. Going at least once per day means that the transit time for our food is as it should be. When it’s too fast, we’re not getting the nutrients out of the food we’re eating, and we’re also going to end up more dehydrated due to the higher frequency of bowel movements. When it’s too slow, we can build up the numbers of bad bacteria in our stomach, as food that sits in the intestines for too long will start to produce gas.
Imagine leaving a piece of meat on the kitchen counter for 2 days. Not going to smell pretty. The same thing takes place in our bodies when we’re constipated, and this can lead to many issues, bloating being the most immediate and common.
Giving blanket statements about what you should do if your bowel movements are disrupted in either way is completely without context. It can be due to fibre intake, food intolerances, stress, illness, or lack of fluids, basically, an extensive list and assessed on a case by case basis.
Regardless of the cause, when it comes to assessing weight fluctuations, with disrupted digestive health the priority should be to ensure that this is first taken care of, through whichever lowest hanging fruit is available.
Weight recording is unreliable at best when bowel movements are disrupted, and can easily sway bodyweight up 2 kilograms (that’s not based on any statistic from an accredited source, simply through anecdotal evidence from working with people and seeing how their weight is influenced when they haven’t been going regularly).
Weight tracking is a slippery slope when it lacks context. It doesn’t mean that it’s useless, quite the opposite, as there’s no way that someone isn’t losing weight if they’re in a deficit. That said, understanding that there are many potential factors that can affect the number can help to keep a more level head when interpreting the data.
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