Numerous recent studies have established that dieters do initially lose more weight when they eat the same number of calories but fewer carbs and more protein. What's more they seem to do it without ill health effects. Even after two years, a 2010 Temple University study reported that those who eat a diet higher in protein had blood fat profiles and other cardiovascular markers that were just as healthy as those who stuck with the traditionally recommended low fat, high fiber diet.
Additionally, Feinman says there is also a small but very real and meaningful effect in how you digest, absorb and metabolize the energy in different types of nutrients -- and it's greater for proteins than it is for carbs.
"For the same number of calories, you add fewer from protein to the body because they get burned during the digestion process," says Feinman.
What irritates Feinman, Bowden and others who agree with their line of thinking, is that the ADA and most mainstream nutritional organizations refuse acknowledge that the composition of your diet and not just the calorie count can impact your waistline, even though there's plenty of evidence to back up these claims. This is where the debate gets more contentious than election year politics
"With so many people struggling with obesity in this country it's a mistake to think that it's all their fault and they aren't trying hard," says Feinman. "Why wouldn't you offer them every single tool that could help?"
Gelbardt counters that the issues are more complicated than the results of studies can often represent.
"While I don't disagree that the body may not process all calories the same in theory, in practical terms it means very little to the average person," he says. "There really isn't much you can do with this information that will help you manage your weight. Your best -- and healthiest -- strategy is still to eat variety of foods and cut back on total calories."
But Gelbardt acknowledges this could change in the future. For example, last year Stanford University researcher Christopher Gardner identified dieting "phenotypes" that indicated genetic differences in how people process each of the different nutrients. These preliminary studies showed that weight loss more than doubled when individuals were correctly matched with a diet -- low fat, low carb or evenly balanced -- based on genetic markers. It's too soon to tell what percentage of the population fits into each category, and results are certainly too preliminary to be useful for individual dieters.
So if you're trying to get the needle on the bathroom scale to point in a favorable direction, whom should you believe? Almost every expert acknowledges that most of us do in fact overeat every type of calorie, and past a certain point it's largely a numbers game. Everyone also seems to agree that we should all be getting more exercise and eating more vegetables -- though there's still some squabbling over fruit. According to Feinman, some fruits have a sugary effect on insulin.
And in the end, no one argues with the fact that for a diet to work, you have to be able to live with it in the long term regardless of where the calories come from.