Evaluation of Intermittent Restricted Eating Using the Interval Weight Loss Online Platform in an Everyday Setting

Abstract

Background/Objectives: Obesity remains a global health challenge. Many commercial online weight loss programs are available, and they have advantages in terms of scalability and access. Few of these programs have been evaluated for effectiveness in a real-world context. This study reports on the weight loss achieved, platform engagement, and characteristics of successful weight loss predictions in subscribers to the Interval Weight Loss (IWL) program. The Interval Weight Loss program promotes intermittent restricted eating in addition to lifestyle changes in diet composition, exercise, and sleep. Methods: Data for 1705 adults subscribing to the program for >30 days between 2019 and 2024 were included in the analysis. A linear mixed model with polynomial terms was used to model weight loss over time with interaction terms for gender and age. Survival analysis was used to model the proportions and time frame of those meeting 2%, 5%, and 10% weight loss targets and the proportion meeting their goal weight. The focus of the analysis was on the effect at 365 days. Descriptive data from a subset of participants (n = 205) who completed a questionnaire about change in lifestyle habits and mood are also presented. Results: Of those who stayed in the program for at least 365 days, 25.4% achieved their goal weight, 17.6% achieved a 10% weight loss, and 62% achieved a 5% weight loss. By 49 days, 50% had lost 2% of their weight. Significant interactions indicated that males and females in their 60s and 70s were the most responsive to the program. Conclusions: The online commercial Interval Weight Loss platform based on intermittent restricted eating resulted in significant weight loss in a cohort of subscribers in a real-world setting.

Keywords: commercial weight loss program; intermittent restricted eating; online weight loss.

Figure 1

Flowchart showing participant flow.

Figure 2

IWL program platform engagement: (a) platform engagement for the total dataset; (b) platform engagement for those subscribing past the free trial period.

Figure 3

Waterfall plot showing the weight change of participants from the largest weight loss to the largest weight gain.

Figure 4

Survival analysis with dropouts censored (in orange) and the two sensitivity analyses where dropouts are excluded after their last weight entry (green) and an analysis where dropouts remain in the dataset with their last recorded weight carried forward. The analysis examined the following: (a) Time until participants achieve goal weight; (b) Time until participants achieve 2% weight loss; (c) Time until participants achieve 5% weight loss; (d) Time until participants achieve 10% weight loss. Only participants in the program after the free trial period are included.

Figure 5

Predicted change in weight from sign-up (%) to 365 days adjusted for age and sex from the linear mixed model with polynomial regression (order = 5).