For half a century, we've been told that saturated fats are bad for our hearts. That belief led to what many now consider the disastrous switch from saturated- fat-filled butter to trans-fat-filled margarine as the bread-spread of choice. It also led to the government's recommendation, through its Dietary Guidelines for Americans, that we limit saturated fat to less than 10 percent of our daily calories. But the latest science has many experts reconsidering saturated fat. A study published in the March issue of the American Journal of Clinical Nutrition, for instance, found insufficient evidence linking saturated fat intake to cardiovascular disease or coronary heart disease. Another study in that issue suggested refined carbohydrates and being overweight are the true culprits. And they're just the latest to suggest that sat fat has gotten a bad rap. Riding high on the wave of saturated fat's rehabilitation, the famous Atkins Diet has been revamped with an eye toward making it easier to understand and maintain. 'The New Atkins for a New You' (Fireside, 2010) allows dieters to eat more vegetables than the old version did. But the diet's core concept _ that carbohydrates, not saturated fat, are what makes us fat _ remains intact. Atkins old and new aim to rejigger metabolisms so people burn their fat, including stored body fat, instead of carbs. The new book, written by Eric Westman, Stephen Phinney and Jeff Volek, guides dieters through four phases, from 'Induction' through 'Lifetime Maintenance.' Atkins followers are encouraged not to count calories and are told that their cravings for carbs will swiftly diminish. Westman says one of the chief differences between the new and old Atkins (made popular in the early 1980s with the paperback release of 'Dr. Atkins' Diet Revolution') is the clarification that the most-restrictive Induction phase accounts for just the first two weeks of the diet and that people with less weight to lose might choose to skip that part altogether. In any case, the Induction phase allows dieters to eat some 'foundation' vegetables: leafy, fiber-filled and unstarchy ones such as cauliflower and spinach. As the diet continues, followers can gradually add carbohydrates until they find an amount they can accommodate without gaining weight. Long-term adherence is one of the problems the new Atkins hopes to solve, giving followers options that include adding more fruits, grains and legumes to the mix. The case for Atkins has been bolstered a bit by two developments. First, the nutrition community has largely accepted that low-fat diets tend not to work because people replace the missing fats with extra carbohydrates. Joan Salge Blake, a registered dietitian and spokeswoman for the American Dietetic Association, notes that the 'Snackwell phenomenon' demonstrated that people assume low-fat cookies are low in calories, too, and they overeat. The second development is the widespread embrace in nutrition circles of the Mediterranean-style diet, which emphasizes heart-healthy fats such as those in olive oil and nuts. Of course, there's not a lot of bacon or butter in the Mediterranean diet, which is favored by the American Dietetic Association. It focuses on a healthful balance of fish, fruits, vegetables, nuts, legumes and that most empty of all carbs, alcohol. Atkins breaks with current weight-management thinking in two notable ways: allowing followers to incorporate as much (or little) exercise as they want, and encouraging sodium consumption. 'If you don't have a salt-sensitive condition like heart failure, salt in the diet is not restricted on Atkins,' Westman explains by e-mail. Adequate sodium intake, the book notes, helps counter the low-carb diet's diuretic effect. The new Atkins, like the old, emphasizes that 'fat is your friend,' even as it encourages folks to eat protein. If you prefer a lean skinless chicken breast, go ahead and have it _ just add a dash of olive oil or a pat of butter. Wrote Westman: 'On Atkins, bacon is a healthful protein! ... The New Atkins is placing more emphasis on the four phases which gradually reintroduce carbs, to get away from the stereotype that `Atkins is all-you-can-(eat)-bacon.' ' The book cites more than 50 studies that support its approach, and its new, more flexible and friendly presentation will undoubtedly make it attractive to former Atkins-ites and new adherents. For my part, until we fully understand the dietary implications of saturated fats and unsaturated fats, I'm not going to put all my, er, eggs in one basket by going gung-ho with Atkins, new or otherwise. On the other hand, the Atkins approach has made many reconsider the basics and un-demonize some dietary demons. So, for the freedom to enjoy a pat of butter now and then, I thank the authors. 