In a significant breakthrough, scientists have identified protein and fiber as critical components for successful dieting, based on a study that led participants to substantial weight loss through a flexible dietary program.
The research, conducted by scientists from the University of Illinois, involved 22 participants who completed the Individualized Diet Improvement Program (iDip) over two years. Throughout the program, participants attended dietary education sessions focused on understanding essential nutrients and developing practical food skills.
Participants were advised to limit their daily calorie intake to 1,500, significantly lower than the commonly recommended 2,000 to 2,500 calories. Additionally, they were instructed to increase their protein consumption to approximately 80 grams (2.8 oz) per day and boost their fiber intake to about 20 grams (0.7 oz).
“The findings clearly indicate that for weight loss diets to be both safe and effective, it’s crucial to increase protein and fiber intake while reducing overall calorie consumption,” said Mindy H. Lee, the study’s lead author and a registered nutritionist, in a statement.
Nutritional experts widely recognize that protein plays a key role in preserving muscle mass during weight loss, which helps maintain or even enhance metabolism, leading to sustainable weight loss. Fiber, on the other hand, promotes satiety and supports gut health, passing through the digestive system without adding to calorie intake.
After one year, 41 percent of the iDip participants were classified as successful, having lost an average of 12.9 percent of their body weight. In contrast, the remaining participants lost an average of just 2 percent of their body weight.
Those who achieved the greatest weight loss consistently consumed higher amounts of protein and fiber. Researchers observed this strong correlation as early as the third month of the study.
While rapid weight loss often results in a loss of muscle along with fat, participants who shed more than 5 percent of their initial weight—largely due to higher protein intake—primarily lost fat cells (78 percent) with minimal muscle loss.
Across the entire group, which was encouraged to increase protein consumption, the average participant lost minimal muscle mass while shedding an average of 16.5 lbs of fat over six months.
Beyond dietary adjustments, the study revealed that mental health played a significant role in weight loss outcomes. Participants with a history of depression—seven in total—lost considerably less weight (2.4 percent) compared to those without depression (8.4 percent). Other health conditions did not appear to have a similar impact on weight loss.
Nutrition professor Manabu T. Nakamura emphasized the importance of personalization in the iDip program, noting that its flexibility allowed participants to tailor their diets to individual needs while equipping them with the knowledge and skills necessary for lasting change.
“Creating personalized, flexible programs is essential for maximizing dieters’ success in both losing weight and keeping it off,” Nakamura stated. “Sustainable dietary change, which differs for each individual, is key to maintaining a healthy weight.”
On average, iDip participants lost 15.2 lbs of fat and reduced their waist circumference by 3.5 inches over 15 months, despite previous unsuccessful attempts at weight loss.
