Weight loss pounding down on you? Basically, there are two solutions -- consume less, exercise more. Sound hard? Not if you let these scientific findings do the heavy lifting.  It's a wonder all of us aren't fat. "Diet and exercise are unnatural acts," says Richard L. Atkinson, M.D., president of the American Obesity Association. "When our ancestors were lucky enough to find food, what did they do? They ate as much as they could, then lay down and went to sleep. I tell my patients that if they want to lose weight, they have to be prepared to do unnatural acts for the rest of their lives -- avoid fun foods and get lots and lots of exercise."  Tough assignment for the overweight half of America. "It's not a simple willpower thing," adds William W. Hardy, M.D., president of the Michigan-based Rochester Center for Obesity Research, sponsor of a recent conference on the physiology of weight. "To say weight control is simply a matter of pushing away from the table is ludicrous."  Nature is a cheat. Sure, calories in minus calories out equals weight, but people of the same age, sex, height and weight can have differences of as much as 1,000 calories a day in "resting metabolic rate" -- one reason your neighbor's gluttony and your own starvation can result in the same readout on the scale. And while people of normal weight average 25 billion to 35 billion fat cells, obese people can inherit a billowing 135 billion. A roll of the genetic dice adds more variety: At least 240 genes affect weight. Luckily, some physiological fudge factors can play to our advantage. Here they are: smart new ways to feel full, get fit and cheat fate, er, fat.  The EAT part ...  Fill up, not out, with these discoveries.  Want to eat ice cream this afternoon? Science says you'll burn it off better if you ate breakfast this morning. People who chronically skip breakfast burn an average 150 fewer calories a day than regular breakfast eaters -- even when both groups consume the same total daily calories, says Mayo Clinic research. The reason: Breakfast eaters awake with a souped-up metabolism; skippers greet each day cold and tired with the "metabolic furnace" set on low till lunch. This little ploy can burn 55,000 calories a year -- the equivalent of losing 15 pounds or eating a monumental 39 pints of Ben & Jerry's Chubby Hubby.  Still hungry? Reach for wet foods, such as a juicy apple or a cup of soup, instead of a dry granola bar or a bag of popcorn. Recent experiments show that water content within foods plays a critical role in weight control. Dehydration stimulates the appetite, and eating foods with high water content makes you feel full better than drinking water to wash down dry foods with the same calorie count.  And if you eat massive servings of low-cal food instead of morsels of calorie-dense food, you'll feel full on fewer calories. In one study, volunteers who ate calorie-dense foods needed 3,000 calories to feel full, but eaters of non-calorie-dense food needed only 1,570 calories. Penn State nutrition researcher Barbara Rolls recently called for food labels to include "calorie per ounce" information. Until that happens, here's a good rule of thumb: Think carrots, not carrot cake. Even though fat is calorie-dense, don't eliminate it. It adds flavor, and if fat intake goes too low, biochemical systems trigger intense pig-out cravings. Advice from the Obesity Council's Atkinson: Keep fat calories to between 20% and 30% of your total, and boost your fiber intake. Not all fats are created equal: Make yours mono and you may end up eating fewer calories. In promising preliminary research, monounsaturated fats -- olive oil, for instance -- appear to work better than other fats in delaying the time it takes you to feel hungry again. So put olive oil on your toast instead of butter or margarine. And, nutty as it seems, studies show that a handful of well-timed nuts so effectively satisfies the appetite that you're less likely to overeat later.  A psychological ploy to eat less: Narrow your choices. A study at Johns Hopkins University confirms what many dieters suspect: The fewer foods in sight, the fewer "triggers" to overeat. Endless sameness is one reason prepared liquid diets work well for many people. Put the principle to work by stocking a smaller variety of foods and eating the same menu (say, chicken breasts, spinach and baked potato) over and over and over. Boring, but not unbalanced. Evidence is overwhelming that the most effective diet is not low-carb, high-protein or any other fad. It's the well-rounded nutrition of the USDA's Food Guide Pyramid (review it at our Web site). And don't go below 1,000 calories a day. One thing you can't cheat on: Don't lie about your calorie intake. Keep a food diary. Too many of us are like the man who believed he took in virtually no calories because he "ate" only coffee. When made to write down exactly what crossed his lips, he was astonished to discover he was getting 3,000 calories a day -- from the sugar and half-and-half he added to his "zero-calorie" java.  The RUN part ...  Exercise is vital. Here are smart ways to sweat.  A study of formerly obese patients who kept weight off for years found that commitment to vigorous exercise is the best predictor of success. In fact, science says it's better to burn calories than cut them. If you eat fewer calories, your body usually compensates by slowing its metabolic rate, leaving you sluggish, cold, plagued by food cravings, but -- alas -- weighing pretty much the same. Burning the same number of calories through exercise can boost metabolism and suppress appetite. Plus, exercise can counteract any fat-guarding legacy you have inherited. A recent study showed the power of this 1-2 punch. Lawrence Berkeley National Laboratory analyzed 35 pairs of identical twins of whom one was a long-distance runner and the other was sedentary. The runners had consistently lean bodies; the couch potatoes' body types were all over the map.  So what's the magic minimum you must exercise? For people trying to lose weight and keep it off, the federal Centers for Disease Control and Prevention recommends a minimum of 30 minutes a day, five days a week; 45 minutes or more, every day, is even better.  You can break it up. Four 10-minute sessions of exercise are as effective as one 40-minute session. If your schedule is too hectic for an uninterrupted workout, try mini-workouts dotted throughout the day. Any exercise is healthful. And when you get a chance, lift weights. A Tufts University study of women who took up moderate weight lifting found they averaged 35% to 76% increases in strength, improved their balance by 14%, and boosted bone density by 1%. The strength-trained women went on to increase their daily activity levels by 25%, compared with an equal decrease in a non-trained control group. Bottom line: Getting stronger encourages you to do more because you can do more.  And the easiest advice of all: Start your fidgeting. A recent study in Science suggests that chronic mini-movements -- fidgeting -- may play a tremendous role in weight. Mayo Clinic researchers deliberately overfed volunteers by 1,000 calories a day. Predictably, some gained lots of pounds, but some gained hardly any. It turned out the latter group fidgeted away up to 850 calories a day, equivalent to an 8.5-mile walk.  If you're not a natural fidgeter, look for ways to foster it. Buy a portable phone and hike around the house when calling. Throw away the remote control and use your whole body when channel surfing. Avoid the elevator; taking the stairs can burn up to 18 calories a minute -- three more than mountain climbing.  Give yourself credit for all of your exercise. Keep a daily activity log that charts "official" and "unofficial" exercise. (How do you count a figdet? Never mind: Count the number of stairs you climb or the number of times you lift your preschooler.) The more activity you document, the more you'll be inspired to do. More is more.  Diet pills: The ultimate cheat?  Most diet products are pretty useless. Some, like ma huang or ephedra, have side effects that can lead to death. Even prescription pills, such as Meridia, can have unsavory side effects and require a doctor's supervision. Still want to try a pill? The Web site vitacost.com regularly tests top natural health products and posts the results online. New on the site: results of independent laboratory tests of 13 diet supplements. Natrol brand 5-Hydroxytryptophan got a perfect score because of a superb lab analysis and substantial medical literature citing 5-HTP's safety and ability to stop cravings. In second place: Nature's Way brand green tea extract, which may boost metabolism and has the added bonus of being a great disease-fighting antioxidant. And four of the 13 products in the test flunked the vitacost.com standards.