Then, a few days later, I got the April 2014 issue of the Nutrition Action Health Newsletter. Its cover story questioned why new health studies seem to flip-flop so often.
Naturally, when a new study overturns everything we've ever heard (e.g., overweight seniors live longer), it garners more press than studies that simply repeat the common wisdom. Headlines tout "earthshaking findings" and downplay humdrum findings. We see this pattern everywhere in the media.
One author told a reporter that a 300-calories difference was "roughly equivalent to an hour of moderate physical activity without lifting a finger."
What's the catch?
For starters, the diets didn't make a difference in pounds gained or lost. If people burned more calories on the low-carb diet -- but didn't lose more weight after a month -- more study is clearly needed.
Even if a low-carb diet led to more weight loss, it's not clear people would stick with the diet. The researchers served the study participants all their meals. The authors conceded that "we did not design the diets for long term practicality."
Another analysis -- the "Pounds Lost" study -- was the largest (811 people) and longest (two years) to test whether people lose more weight on low-fat, low-carb, or high-protein diets. No one diet stood out by producing significant results. Participants lost an average of 13 pounds after six months and kept off an average of nine pounds after two years, regardless of which diet they followed. The lead author said, "Ignore all the hype about diets that make pounds melt away. Losing weight comes down to how much food you put in your mouth."
This study has been criticized because it couldn't guarantee that participants maintained pure low-fat, low-carb or high-protein diets over the course of the two-years study. The researchers said, "If participants in a study can't stick with a diet, it's even harder for people to do it on their own."