Ludwig defended the weight loss, saying that, unlike most weight-loss studies, his numbers included people who could not comply with the diet and left the study.
"Among people who complied with the diet and stayed in the study, the differences were even greater," said Ludwig, citing an average weight loss close to 10 percent for people who stuck with the low-glycemic diet for 18 months.
Ludwig also emphasized that people on the diet were able to maintain weight loss after 18 months -- a time when most dieters have returned to their original weight.
"It may be less fast, but it's more sustainable," he said.
"David Ludwig is an international authority in this area and does high quality work. His bias, however, creeps into this report," said James W. Anderson, a professor of medicine and clinical nutrition at the University of Kentucky.
Anderson said he feels the study was not properly designed to back up Ludwig's current claims.
Specifically, Anderson believes the number of dieters in the study to be too small to determine that we have reached a time for personalized dieting.
Of the 73 original participants, only 35 completed the study and had blood insulin levels available for analysis (51 completed the study overall). Those 35 were further spread into four separate diet groups.
"You don't design a study with nine subjects in one group," Anderson said.
"More needs to be done, but this is a step in the right direction to identify what dietary approaches will work with one patient instead of another," said Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center.
Sandon feels Ludwig's study represents a valuable trend in dieting toward finding different diets to fit different patients.
Despite the small size of the study, Sandon felt enough past research had shown similar enough results to justify Ludwig's conclusions, and she is considering advising certain patients to undergo blood insulin tests.
Ludwig was equally sure of his results.
"[There's] no reason to believe the findings won't be representative," he said. "We have a great deal of confidence that these findings are real."