Holly Lofton, MD, director of the Medical Weight Management Program at NYU Langone Health, and Eduardo Grunvald, MD, FACP, medical director of the UC San Diego Weight Management Program, talks about fluctuations in weight mainly due to fluids as well as fat loss and gain. It’s harder to put on muscle than it is to put on fat. Dr. Grunvald noted initially that if we’re talking about longer-term change in weight, “we’re talking about fat weight, although muscle weight can also fluctuate.” There are instances, too, when medical disorders will affect your weight, which we discuss ahead.
Dr. Lofton said that weight tends to go up during the day — as much as five pounds — because we eat and drink and don’t eliminate all of it. This, she said, is the obvious reason. It also has to do with sodium in certain food, which draws in water. Things that are rich in sodium (potato chips, for example) keep water in the bloodstream, which makes our weight on the scale increase. “We urinate less with the salty food and thus hold onto more water,” she explained. Other things that may affect weight include physical activity. “Every time we move, our muscles contract. They use carbohydrates and water to contract and that can lead to some temporary swelling, which can manifest as weight gain on the scale,” Dr. Lofton said.
Seeing three, maybe four, extra pounds on the scale by the end of the night, Dr. Lofton said, is normal. Anything greater than five pounds she considers to be abnormal. Dr. Grunvald agreed. Daily weight fluctuation due to water retention in a healthy person usually only registers as a few pounds, he said. On the other hand, patients who have kidney, liver, or heart disease may hold onto more water. “Even some pituitary issues may affect water retention or the ability of the kidneys to produce urine, and thus, they hold onto more fluid,” Dr. Lofton added. She also pointed to pregnancy as another instance where retention of fluids would increase.
In addition, sometimes people can have leg swelling throughout the day if they tend to be on their feet a lot. “Because they’re in an upright position, they can get what’s called dependent edema, and if their blood vessels aren’t as readily able to push fluid back up from the lower extremities, then that can cause it to pool and that causes visible swelling, which can look like weight gain on the scale.” This is referred to as vascular or venous insufficiency. If it happens to you, resting and elevating your legs helps, Dr. Lofton said.