You sodium intake can significantly influence water weight. Sodium pulls water into your cells, so if you consume more sodium than normal, your body will temporarily retain water until fluid balance and sodium concentration are normalized. This can bump up your weight as much as 3.3 pounds (1.5 kilograms) according to one controlled study.
Before you look back at your food journal and cut sodium completely, know this: Sodium has many vital roles such as maintaining blood volume, regulating nerve and brain function, and enabling muscle contractions. The key is to monitor your sodium intake but not cut it out completely. A minimum target for sodium is between 1,500-2,300 milligrams per day, and more if you sweat a lot during your workouts.
For example, in an hour of profuse sweating, you might lose 4 cups (1 liter) of water and 1,000 milligrams of sodium. This means you need closer to 2,500-3,300 milligrams of sodium in order to replenish electrolytes.
To keep fluctuations in sodium intake from spiking your scale weight, keep your sodium intake somewhat consistent and within the healthy range for your training level. Avoid weighing yourself for a couple days if you splurge on salty processed foods and restaurant fare, since you will likely be holding on to at least a couple pounds of water weight.
2. You’re Holding Waste
This should be obvious, but if you just ate a large meal or haven’t had a bowel movement in a couple days, your scale weight will be high. This is why I always recommend weighing yourself first thing in the morning, fasted, after going to the bathroom.
If you’re not having regular bowel movements (daily is the standard of regular), make sure you’re getting 25-40 grams of fiber per day and a gallon of water daily. You might also want to try adding a daily probiotic supplement. High-fat foods, dairy products (if you’re lactose-intolerant), and too much fiber can cause constipation when consumed in excess, so don’t go overboard.
Some prescription pain killers, antidepressants, and blood pressure medications can also cause constipation. Stool softeners and laxative teas may offer a temporary solution, but if constipation is an ongoing issue, talk to your doctor.
3. You’re Carbed Up
If your carbohydrate intake was higher than normal a day—or even three days—before you stepped on the scale, your body will have stored those extra carbs as muscle glycogen.
For every gram of muscle glycogen stored in skeletal muscle, your body stores an estimated 3-4 grams of water. This may seem like a small number, but it can really add up! Between your muscles and liver, the average person has the capacity to store around 500 grams of glycogen—and that’s before any fat storage occurs.
Let’s just say you enjoyed a bunch of cake and pasta for your “treat meal” and came out at 300 grams of carbs for the day. Assuming all 300 grams of carbohydrate are stored as muscle glycogen, you just gained 1,200-1,600 grams combined glycogen and water weight, which equates to 2.6-3.5 pounds on the scale. That’s all without one iota of fat storage!
Now, we’re always carrying around some glycogen weight. So if you want the scale to give you a more accurate picture, plan your weigh-ins either the morning of a high-carb day (before eating), or at least four days after.
4. Your Hormones Are Punishing You
High levels of cortisol can increase sodium retention, which as we’ve learned, can cause water retention. Many factors can lead to elevated cortisol levels, including sleep deprivation, stress, overtraining, and extreme caloric deficits.
Elevated levels of estrogen can also lead to water retention. This is why women experience bloating and water retention in the days leading up to their menstrual cycle, usually 2-5 pounds. In other words, if you’re about to start your period, don’t freak out if the scale shows a weight increase despite good nutrition and consistent workouts. Weigh in again next week, and everything should be back to normal.
Estrogen levels can also fluctuate during menopause due to estrogen-replacement therapy. Estradiol, a form of estrogen used to treat symptoms of menopause, has been shown to lead to weight gain due to water retention.
In this case, it is better to put the scale aside and focus on nourishing your body with nutritious foods, consuming an adequate number of calories for weight maintenance, and exercising regularly.
5. You’re Recovering From A Hard Workout
Delayed onset muscle soreness (DOMS) is the intense muscle soreness you begin to experience 24-48 hours after a new or especially rigorous workout. It’s usually worst 48-72 hours after exercise, and is usually gone within 3-5 days. DOMS is the result of microscopic structural damage to muscle fibers, and it can result not only from weight training, but also from just about any type of physical activity. That hot yoga class or pick-up game of soccer? Yeah, they can give you serious DOMS.
These may be some reasons why your scale is completely inaccurate. Body composition scans that measure muscle mass, bone mass, fluid, and body fat are more accurate.