Poor sleep causes a “hydration hormone” shortfall

95% of women over 40 are dehydrated, says Howard Murad, M.D., author of The Water Secret. “As we age, stress, poor diet and environmental toxins damage the body’s cell membranes, weakening their ability to hold water.” Why that’s a problem: “This damage leads to subclinical dehydration and the exhaustion, brain fog and weight gain that follow.”

Sleeping fewer than six hours raises the risk of dehydration by 60%, say scientists at Penn State University.

“The hormone vasopressin, which regulates the body’s water balance, is released in greater amounts after six hours of sleep,” says Michelle Schoffro Cook, Ph.D., author of 60 Seconds to

Slim. “So if you’re sleeping six hours or less, your vasopressin levels drop, worsening dehydration—and fatigue.”

“Unless you’re dangerously dehydrated, it often goes undetected,” says integrative medicine specialist Dana Cohen, M.D., author of Quench. Her advice: Drink half your weight (in ounces) of water daily. And try the steps below to help your body better absorb water.

Add lemon, lime or cucumber to water, suggests Schoffro Cook. “This changes water’s surface tension so it can better penetrate cells and hydrate.”

Enjoy healthy fats. Saturated fats harden cell membranes, so cells can’t absorb water, says Dr. Cohen. But good fats (olive oil, avocados, flaxseed and fatty fish) keep membranes permeable to improve cells’ water absorption.

Practice micro-movements. “We need to move to push fluid into our tissues,” says Dr. Cohen. “Micromovements, like squeezing your muscles while in the car or at your desk, will move water through your fascia, the connective tissue responsible for hydrating your body.”