A low-fat diet will help you lose weight. Or is it a low-carbohydrate diet? Pore over decades of research and dozens of studies over this debate and you're likely to be confused about the best way to go about reducing your waistline.
"I think lowering carbs is what you should do," says Heather Straight, a Pleasant Hill, Calif., mom of three who says she's tried several diets. "At least, I think so."
She may be onto something. Maybe.
Gary D. Foster, director of the Center for Obesity Research and Education and professor of Medicine and Public Health at Temple University in Philadelphia and his colleagues published a widely circulated study in August that followed 307 dieters and concluded either a low-fat or low-carb diet can help you lose weight, but a low-carb diet is, perhaps, better for "good cholesterol" values, or HDL.
But is Foster a convert to a low-carb dieting approach, popularized by cardiologist Robert Atkins in the 1970s?
"I think it's a disservice getting people to worry about the minutia of diets," Foster says. "There are pieces of dieting that we know work. One, track what you eat. Weigh yourself often. Make changes behaviorally that allow you to eat healthier."
In fact, many diet experts, including local doctors, reel over the low-fat versus low-carb dieting discussion. It misses the point, they say. Americans, 60 percent of whom are either overweight or obese, need to eat less and lower the amount of sugar in their diets, through reducing carbs and sweets. They need to eat real foods, not overly processed, sugar-added treats. And they need to think about what they're eating instead of mindlessly consuming whatever tastes good.
"Honestly, it's more than just a question of should you go low-fat or low-carb but more of the quality of what you eat," says Sooji Rugh, a doctor with the San Jose, Calif., weight-loss centers Greenlite Medicine. "Not all carbs are the same and not all fats are the same."
For example, saturated fats found in cheeses and fatty meats can contribute to heart disease, although protein rich diets are considered good for people. Carbohydrates also differ: The sugar and white flour in white breads are considered less healthful than the whole wheat flour in some wheat breads. If you are trying to lose body fat on a low carb diet, 20 to 70 daily grams are recommended, depending on your level of activity. People need some carbs for energy, and most healthful fruits and vegetables contain carbohydrates.
The promotion of a low-fat diet started in the United States around the 1950s, fueled mostly by Nathan Pritikin. Pritikin was diagnosed with heart disease and began his low-fat diet along with exercise and resolved the condition. He popularized the results in his 1979 book, "The Pritikin Program for Diet and Exercise." Low-fat diets became all the rage.
To lose weight on a low-fat diet, weight loss experts say total fat intake should be no more than 30 percent of total calories. The problem now, says Greenlite's Rugh, is that many foods in the grocery store that are labeled "low fat," such as yogurts, are loaded with sugars to keep them appealing to the palate.
"If you lower the fat content in the processed food, it tastes horrible unless you do something else, so they heightened the sugar content," Rugh says.
The World Health Organization and the American Dietetic Association recommend that calories from sugar not exceed more than 10 percent of our total calories, she says.
"You have one can of Coke, and you've exceeded that," she adds.
The problem with sugar is that, simply, it spikes insulin. And when insulin levels are raised, people accumulate fat.
"At one point, your pancreas (which produces insulin) will start wearing out and then you're looking at diabetes two," says Ranveig Elvebakk, an Oakland, Calif.-based doctor and nutrition expert who is a long-standing member of the American Society of Bariatric Physicians.
She likens the question of a low-fat versus low-carb diet to a nonsensical proposition.
"It's like, if I have a yellow car, what type of fuel do I put in it? It doesn't make any sense," she says.
Insulin spiked by sugars and carbohydrates - which are processed by the body into sugars - promotes weight gain, Elvebakk says.
"Ninety percent of the weight problem we have is caused by eating sugar, not fat," she says. "If you want to lose, gain, or stay the same weight, then you need to understand the mechanics of weight loss. And when you raise your blood sugar, you raise your insulin and insulin stores fat."
Perhaps the best-known version of a low-carb diet is the Atkins diet, which had a resurgence in the early 2000s. It's a common misperception that people can eat butter-laden steaks and lose weight healthfully. There are good fats and bad fats - fats in nuts, olive oil and fish are better than most other fats.
"We can eat a small amount of fat," Elvebakk says. "People need about three tablespoons of olive oil a day and some omega threes."
And the American Heart Association criticizes low-carb diets, saying the food restrictions in them often starve the body of essential vitamins and nutrients.
Dr. Diana Wright of Bay Area Nutrition, whose offices are in Gilroy, Calif., lives by the adage that if you want to lose weight, you need to eat less and exercise more instead of worrying about fats and carbs.
"You need to look at how you're eating now. Sometimes you can turn to a peer or a book, sometimes you need to turn to a professional to give you some advice about where you can make reasonable changes in your diet," she says.
She also doesn't want people to forget about exercising either. People are designed to be physically active, she says, and sitting hours behind a desk doesn't promote good health.
"We eat more now and exercise less. It's like you lose a job and you start spending more money. That's backward," Wright says.
Wright quotes popular author and University of California-Berkeley professor Michael Pollan saying Americans need to "eat food. Not too much. Mostly plants."
"People who control their weight also don't skip meals. They always have breakfast. They are exercising about an hour a day. They don't take holidays from their diets and they weigh themselves regularly," she says, adding that many people may benefit from a diabetic diet plan that limits sweets, promotes eating often and considers how often and when you eat carbs.
Lifestyle change is the key to losing weight, the experts say.
"Successful weight loss and maintenance is having the mind-set to do it," Wright says.
Explore further: Health care organizations see value of telemedicine