“Learn how the food you eat, the way you exercise, your sleep quality, and your stress patterns affect your blood sugar (glucose),” says Signos.com, one of a handful of companies that sell continuous glucose monitors (CGMs). “This is the Signos approach to healthy weight loss.” Many people with type 1 diabetes—they produce no insulin—wear CGMs to let them know if their blood sugar is too high or low. But it’s not clear if anyone else needs the devices, especially if weight loss—not controlling blood sugar—is the goal.