If it’s not hard enough to lose weight, keeping it off can be even tougher. By some estimates, up to two-thirds of dieters regain more weight than they lost within four or five years. To beat those odds, and keep the scale steady, try these science-backed strategies:Stick to a low-GI dietWhen compared with low-carb and low-fat eating plans, a low-glycemic-index (GI) diet may give you the best chance of keeping weight off in a healthy way. Scientists involved in research published in the Journal of the American Medical Association looked at the three diets and found that the low-carb plan helped burn the most calories, but it also appeared to raise risk factors for heart disease. Participants on the low-GI diet burned more than 100 more calories a day than the low-fat group, without harmful heart effects.A low-GI plan is similar to Mediterranean-style diets, emphasizing foods with slow-digesting carbohydrates, such as beans and lentils, non-starchy vegetables (like broccoli), fruit and whole grains, as well as lean proteins and healthy fats like olive oil.Keep working outYou increased your physical activity to lose the weight. To maintain your new look, successful dieters say you have to stay the course. According to the National Weight Control Registry, which tracks the habits of more than 5,000 people who have lost and kept off weight, 90 percent of those surveyed report exercising about an hour a day. Break it up if you need to: Take 20-minute brisk walks in the morning, afternoon and evening — the effect is the same.Track your weightand daily food intakeIt may seem tedious, but it can help monitor your progress and spot potential pitfalls. Step on the scale about once a week (morning is the best time) and log your numbers. If the pounds creep back on, check your food journal. It can help identify patterns and habits derailing your success. Then you can make changes — like packing healthy foods for your road trip, or taking a quick lap around the office on a break.Remember why youwant to stay slimYou look better, you feel healthier and in control, you have more energy, or you can fit into your favorite dress. Whatever the reason, taking a minute to remind yourself every day why it’s worth the effort is a tactic that can help you keep the weight off, according to a survey of more than 1,100 people who maintained weight loss.Enlist the help offamily and friendsSupport from loved ones is key to keeping you motivated. Be specific about what you need to stay on track — brainstorm healthy menus or recipes, invite them to an exercise class or along for a walk, even ask that they don’t offer you your trigger foods.• The Doctors is an Emmy-winning daytime TV show with pediatrician Jim Sears, OB-GYN Lisa Masterson, ER physician Travis Stork, and plastic surgeon Andrew Ordon. Check www.thedoctorstv.com for local listings.