Maybe you noticed your weight wasn’t what it usually is at your recent doctor’s appointment. Or you went to put on your favorite pair of jeans and they didn't fit the way they usually do.
You haven’t changed your diet or exercise routine recently. So what gives?
More than likely, you’re experiencing some weight fluctuations.
“I get a lot of questions from patients who noticed they gained a couple of pounds and want to know why. I try to reassure people that in general it’s really normal,” says Dr. Sarah Halter, a primary care and healthy at every size (HAES)-friendly doctor who sees patients at UW Medicine Primary Care at Factoria.
If you’re concerned about weight fluctuations, here’s what you need to know.
How does the body regulate weight?
Many systems within the body play a role in maintaining (and sometimes changing) weight.
Your brain and the hormones circulating in your body stimulate and suppress appetite. Your gut absorbs nutrients and pushes along what it doesn’t need. Your liver and muscles regulate your blood sugar levels, and your kidney and adrenal glands manage how much water and salts are in your body.
In general, the body tries to keep its processes balanced so they work well together; this is called homeostasis.
Just like your blood pressure or heart rate may increase if you’re stressed or excited, your weight can fluctuate a little depending on what else is going on in your body, says Halter.
Because of all these different processes influencing weight 24/7, weight fluctuates not just throughout life but also throughout the day.
“The average adult’s body weight fluctuates between 2.2–4.4 pounds over a few days,” says Dr. Nicole Ehrhardt, an endocrinologist at the UW Medicine Diabetes Institute.
What causes weight fluctuations?
That number you see on the scale is influenced by so many things: what you eat, sure, but also how often you exercise, what kind of exercise you do, how much muscle you have, what medications you take, your hormones and your health behaviors.
For example, people taking birth control or antidepressants often report small amounts of weight gain, Halter says, though it can be difficult if not impossible to determine if a few extra pounds are due to a medication or some other factor.
As people age and hormone levels decrease, they may lose a little weight; according to Ehrhardt, men often lose weight after age 55 and women after age 65.
Weight also changes due to changes in behavior. For example, Ehrhardt says research has shown people tend to weigh more on weekends and less during the week. It’s also common for people to gain weight during holidays and during colder seasons, she says.
For people who menstruate, weight fluctuations can happen during your cycle, too.
Even seemingly simple decisions can affect your weight at any given moment. Not drinking enough water can cause your body to retain more water and thus weigh a little more.
For example, someone who eats a lot of food that is high in salt and carbs — which retain water — can make their body itself retain water weight, whereas people who exercise and sweat a lot often lose a lot of water weight.
Being bloated can affect weight, as can whether or not you’ve had a poop recently.
When should you see your doctor about weight fluctuations?
There’s no specific right amount of weight fluctuation, Halter says. How much your weight fluctuates from day to day and over time depends on all the unique factors that make you, you. What’s normal for one person may not be normal for another.
That said, dramatic weight loss or weight gain in a short amount of time may indicate an underlying health issue.
“Weight loss of 5% or more of total body weight in one month without a change in lifestyle habits would be a red flag to discuss more with your doctor,” Ehrhardt says.
So, for someone who weighs 140 pounds, losing or gaining seven or more pounds each month would be reason to visit the doctor’s office.
Even if you aren’t gaining or losing weight rapidly, there’s no harm in seeing your doctor if you’re concerned or just want a better understanding of what might be going on in your body.
Track your weight over longer periods of time — not just a few days or a week — and bring this information to your doctor, Halter says.
“If someone is worried, I never mind them just coming in to talk about it,” she says.