The purpose of this article was to answer the question of whether people who want to reduce their body weight can achieve different results depending on their baseline BMI and whether the rate of weight loss is constant over the months of intervention. The study included 400 individuals aged 19 to 55 years with a mean BMI of 31.83 ± 4.77 (min 25.1 max 51.8). Men comprised 190 subjects and women 210 subjects. The participants were divided into three groups with the following BMI: overweight, class 1 obesity, and obesity class > 1 (class 2 and 3 combined). BMI groups were randomized by gender, the number of trainings per week, training time, intervention length, and intervention type. The online intervention consisted of a 15% energy deficit diet and training. Over the 12-month dietary intervention, overweight subjects reduced average body weight by 16.6%. The group with class 1 obesity reduced body weight by 15.7%. The group with obesity class > 1 reduced mean body weight by 15.4%. The relative weight reduction in the overweight group was significantly greater than in the other obesity groups (p = 0.007). In all groups, the rate of weight loss from month-to-month was statistically significant (p = 0.0001), ranging between 0.6 and 2.6% per month. The results indicate that overweight individuals are likely to experience a percent greater weight loss as a result of a comprehensive lifestyle intervention. Regardless of baseline BMI, the observed weight loss was consistent from month-to-month throughout the 12-month period, which may indicate that the diet, as well as, the training plan were properly tailored to the subjects’ needs and that they were highly motivated to participate in the program throughout its course. Properly conducted lifestyle intervention enables significant weight loss regardless of baseline BMI values.

The problem of obesity is affecting an increasing number of people worldwide. The COVID-19 pandemic and the required social distancing, which make it impossible to see a dietitian, present new challenges and require the development of new ways of working with overweight individuals. Based on research and practice, dietetic services are beginning to shift from in-office consultations to a form of online consultation using mobile apps and websites. This literature review aims to critically analyze the scientific evidence for the effectiveness of interventions targeting weight loss in overweight or obese individuals focusing on behavioral and online interventions. The data from the presented studies suggest that the effectiveness of online interventions to control body weight is high enough to be used in nutritional education and in weight reduction or maintenance. The main advantage is a wide access to them for the public.