Why Your Weight Fluctuates 5 lbs in a Day
If you gained 3 pounds overnight, it’s probably not fat.
When you’re on a weight loss journey nothing is more demoralizing than seeing your weight jump up by 5 lbs in a day. It feels like failing but it’s actually all about osmosis.
I forget his name now, but a few years ago I saw a patient in the urgent care regularly for various health problems related to obesity. He’d weigh in at 385 one day and 360 just two day later.
Welcome to the Physician-Led Health Coaching weekly newsletter. I’m Dr. Ashori, a board-certified physician & health coach. I help people fix brain fog, fatigue, and stubborn weight before they turn into real disease.
#1. Water Retention
Women understand this much more intuitively because a menstrual cycle creates bloating due to fluid retention.
Progesterone blocks aldosterone receptors, which increases salt retention, and then estrogen drives thirst, which increases water retention.
Even without hormonal influences your thirst may be affected by temperature, humidity, exercise, and whether you’d had plain water versus fruits and vegetables.
#2. Salt is Powerful
Salt hides in plain sight everywhere these days. I had oatmeal the other day and the chef told me how much salt he puts in. Wow! No wonder it was so good.
Bread, pasta, pastries, canned foods, and restaurant foods hide a lot of salt as well. While you should be able to excrete it through the kidneys, your body can handle only so much.
There’s only so much extra sodium your body can filter through the kidneys and excrete in the urine.
#3. Food & Waste Build up
Your intestines can hold an impressive amount of mass. You would think that it should protrude by quite a bit if it’s holding on to an extra 5 pounds of food and waste. But you have a lot of “space” in the gastrointestinal tract and any excess weights will get tucked into your pelvis.
That’s why some people develop urinary obstruction, pelvic pressure, pelvic organ prolapse, and other pelvic problems when they aren’t able to evacuate their bowels adequately.
#4. Stress Affect Hormones
Most hormones have some downstream effect on water and sodium balance. And it’s not immediate. Your poor sleep on Monday may have you retaining water all the way through Friday.
Sympathetic activation, the RAAS system, vasopressin, and cortisol are affected by your stress and sleep quality.
Focus on Your Weekly Average
So, are you tracking your weight in hopes of improving your body composition? Focus on your average weekly numbers and less on daily values.
If I notice a lot of weight fluctuations in my patients I like to look at their salt intake, stress levels, and hydration. Usually we discover the source somewhere here.
I wrote this article for one of my health coaching clients who has been really frustrated with his yo-yo-ing weight. Once I explained this to him he stopped weighing himself weekly. That’s success.
And the only reason excess body weight fluctuations are important to me is that there is data to show that a lot of weight fluctuations could increase health risk. This mostly became apparent once someone’s body weight fluctuated by more than 7%.
Disclaimer:
Dr. Mohammad Ashori is a U.S.-trained family medicine physician. The content shared here is for education and general guidance. It is not personal medical advice, diagnosis, or treatment, and it does not create a doctor-patient relationship. Humans are complicated and your personal details matter. Your healthcare team is your best resource before making medical decisions, changing medications, or managing symptoms. This information is to help you add more depth to those conversations.
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