The average adult’s weight fluctuates up to 5 or 6 pounds over the course of the day. Like literally. That is A LOT!
Of course, if you record your scale weight, fluctuations from day to day should not be this high.
If you stick with the same time and same routine every time you weigh yourself, your weight should be much more consistent.
But no matter how consistent you are, there will always be some sort of fluctuation, particularly in females.
That is why we want to focus on the weekly average and there is no need to panic if the scale moves in the "wrong" direction from one day to another, because fluctuations from 1-2 lbs within a day are totally expected.
Obviously food and water intake has an effect:
High-salt foods can cause water retention. The extra water adds up to pounds on the scale. Some people are very sodium sensitive and may retain more water, while others are less sensitive.
Many of us don’t overuse the salt shaker at mealtime. But sodium can hide in unexpected places. Cold cuts, frozen meals, and savory sauces are often high in sodium. Canned soup is another common culprit. And of course restaurant foods tend to be higher in sodium too.
If you love bread, pasta, rice, and other starchy carbs, the weight gain you see on the scale may be related to your carb intake. Not to actual fat gain from carbs! But for every gram of carbohydrate you consume, your body retains about three-four grams of water in order to store the fuel source.
For that reason, if you eat a very high carbohydrate meal, your body weight is likely to increase because of the water weight. In addition, many refined carbohydrate foods are also high in sodium. For example, a spaghetti and meatball meal with Parmesan cheese may cause you to retain water due to the high carbohydrate AND salt content.
3. Food Weight
Food intake will, of course, cause your weight to increase slightly while the food is processed by your body (that is why you should always weigh in before you eat or drink anything). The food you consume can weigh a few ounces per meal, up to a few pounds per day. The water in food can cause your weight to increase as well. So what happens to all of that weight? Naturally, it doesn’t automatically stick to your thighs. The calories in food are either used to fuel your body’s natural processes, the energy is stored to be used later and of course some of it is excreted in waste products.
4. Bowel Movements
You’re likely to see some fluctuations on the scale due to bowel movements. How much does your poop weigh? In a research study, investigators found that you might produce 125 to almost 170 grams of stool per day. That’s about half-pound of poop.
Even when you lose stool weight, there will still be digestible material in transit. Normal physiological fecal transit time is estimated to vary between 40 and 60 hours, with an optimal whole gut transit time of 24 to 48 hours. Transit time can be slowed or sped up through fiber.
It seems pretty logical that water intake plays a role, but sometimes we don't consider our sweat rates, dehydration etc.
When you drink alcohol, it is possible that you could notice an immediate weight decrease as it acts as a diuretic to some extent, causing you to urinate more than usual while drinking. However, this imbalance may also cause your body to retain fluids from the beverages you consume and from food that you eat. Many times when we drink we overeat, particularly salty foods that cause water retention. The end result is that it is very possible to see a weight increase after drinking.
Other factors aside from food and drink play a role too:
Again, not necessarily in the way you are expecting.
Many if not most forms of exercise cause some sort of temporary inflammation (through initial muscle break down for example), which can cause your muscles to retain water. Why does this happen? Your muscles store and use water to repair the damage. When you create and repair these micro tears your muscles become larger and stronger. This is why after a particularly "hard" training session your weight might be up.
6. Inflammation in general
This can be any kind of injury, bruising, wound healing, illness, after a vaccination (most people see weight increases of 2 lbs after their second CoVid vaccination for a couple of days)...but also after random things like if you eat a lot of inflammatory foods (highly processed foods) or get a sunburn (inflammation).
This is a big one, particularly for the ladies.
Let's start with the generic ones though.
May not comes as a surprise, but if cortisol/ stress is high, it is very likely weight is up (or at least not going down) and not even due to stress eating or lack of bowel movements (which are often "side effects" of high stress), more because cortisol also leads to water retention and potentially higher levels of inflammation throughout the body.
The other most weight influencing hormones for women are estrogen and progesterone:
As a quick refresher, estrogen levels increase before ovulation (midpoint of the cycle), then drop down during the beginning of the luteal phase (after ovulation, before the next period), which usually leads to water retention. As estrogen levels decrease during the luteal phase, progesterone levels increase, leading to another increase in water retention. By the time the period starts, estrogen and progesterone levels drop back down and water retention decreases with each day. This is how it works theoretically, but practically, this can be different from woman to woman. Some research suggests that women can perceive water retention to be the greatest during the first day of their cycle.
Lack of sleep is a stressor on the body on its own (higher cortisol), which can also lead to other hormonal adaptations that influence weight, for example by impacting our thyroid but also by affecting our hunger and satiation levels as well as reducing our energy output (so make sure you aim for your 7+ hours a day :).
Various forms of medication, whether for prescription or simply things like aspirin or ibuprofen, can affect weight also.
Lastly, how should we weigh ourselves to avoid any additional errors?
- use the same scale every time
- weigh yourself every time at the same time of day, ideally right after you have woken up and been to the bathroom
- weigh yourself without clothes on
- weigh yourself 2-3 times a week to get a good average (if you only weigh yourself once a week you may catch yourself out on a higher day and get discouraged)
BUT, daily weigh ins can be a trigger for some people. If you find that it tends to "ruin your whole day" weighing in daily isn't necessary. Nonetheless, you may want to get to the bottom of WHY this is such a big trigger for you and work towards simply seeing it as data.
- incorporate other ways to track progress or make sure you are maintaining your physique such as pictures, measurements around waist etc, body scans or simply keeping a tap on how your clothes are fitting.
To sum it up:
Daily and even weekly weight fluctuations are totally normal. If you ever feel discouraged by the scale being "stuck" somewhere or temporarily going up, please consider all of the factors above and hopefully that will put things into a more logical and less emotionally attached perspective for you.