The "More Health, Less Diabetes" project is a hybrid randomized controlled trial to prevent type 2 diabetes in individuals at risk through structured exercise and lifestyle education. While exercise benefits for people with diabetes are well-documented, evidence remains limited on the effectiveness and cost-effectiveness of in-person and home-based exercise programs in a prediabetic population. This study aims to understand the clinical and cost-effectiveness of a three-arm RCT (online, in-person, and a control group) in people at high risk of developing T2DM. This 12-month program includes six months of supervised exercise (3 times/week) and a six-month follow-up. During the first six months, both intervention groups will attend educational sessions to improve health literacy and promote healthy habits. The primary outcome will be 2h glycemia in an oral glucose tolerance test. Secondary outcomes include other aspects of glycemic control (HbA1c, fasting glycemia, HOMA-IR, Matsuda index), 24-hour movement, body composition, vascular health, physical fitness, and cost-effectiveness using a social return on investment approach.

Introduction

Diabetes is a major public health concern affecting approximately 11.1% of the adult population (588.7 million people), with projections suggesting an increase to 852 million by 2050. In Portugal, diabetes affects approximately 14.1% of the population between 20-79 years, with an additional 28.6% of the Portuguese population having intermediate hyperglycemia. These alarming values result in a financial burden for the Portuguese healthcare system, with annual costs ranging between 6-7% of total Portuguese healthcare cost.

On this note, there is evidence that 70% of people with intermediate hyperglycemia tend to develop type 2 diabetes mellitus (T2DM) in a 10- year follow-up . Risk factors, such as higher BMI and waist circumference values, physical inactivity, unhealthy diet, and poor health literacy, are directly associated with the development of T2DM. Furthermore, from the early stages of pre-diabetes, there is strong evidence of structural and functional vascular changes, which are known to increase in the medium to long/term micro and macrovascular complications.

From an economic and public health perspective, exercise interventions in a community setting are worth investing for T2DM management and prevention. The Diabetes Prevention Program (DPP) reported that 5-7% individuals who met the physical activity goals reduced their incidence of T2DM by 44% - even without weight loss. The 15-year follow-up study of the DPP has also provided evidence of the superior impact of a lifestyle intervention for preventing the development of DMT2 compared to just medication. Furthermore, our group has also shown the importance of exercise in improving health-related biomarkers in people with T2DM. Despite its known benefits, evidence suggests that comparability across exercise interventions is limited due to several issues, such as heterogeneity in intervention type, design, and delivery. For instance, studies have explored the impact of online or in-person regimes to address how lifestyle interventions should be delivered. The current body of literature on online interventions suggests that the improvements in health-related outcomes and adherence may be compromised in the medium to long term. However, online interventions are known to be more scalable and less expensive than in-person programs. On the other hand, evidence from national in-person programs, such as the "Diabetes em Movimento" program, has shown that community-based exercise programs can significantly improve cardiometabolic parameters and still be cost-effective in people with T2DM. This program is currently implemented in 52 Portuguese municipalities. Despite the effectiveness and cost-effectiveness of such exercise programs on the T2DM population, there is a gap of experimental evidence of how in-person or online lifestyle programs impact those at risk of developing T2DM. Thus, it is crucial to develop a proof-of-concept, evidence-based exercise program tailored to individuals at risk of T2DM that can ultimately be scaled to reduce the burden of T2DM at a population level. Implementing a hybrid randomized controlled trial would allow for a comprehensive cost- effectiveness evaluation, helping to determine whether online or in-person delivery yields the most economically viable and clinically beneficial outcomes.

Aims

1. To analyze the clinical effectiveness of a 6-month online regime vs. in-person lifestyle intervention vs. controls on post-prandial 2h glucose in an OGTT in people at an increased risk of developing type 2 diabetes and its impact at a 12-month follow-up period.

Secondary:

1. To evaluate the cost-effectiveness of the intervention with exercise and educational sessions, using a social return on investment approach (SROI) in an online regime vs. an in-person regime vs. a control group at the 6-month and 12-month periods
2. Assess differences at the 6-month intervention and 12-month follow-up period in other aspects of glycemic control (HOMA-IR, Matsuda index), body composition regional and total outcomes, structural and functional vascular health, handgrip strenght, 24-hour movement variables, and quality of life in the different intervention arms (e.g., In-person, online, and control).

Recruitment

Participants will be recruited for an interventional study targeting individuals with prediabetes or a high-to-very-high risk of Type 2 Diabetes, based on risk stratification using the FINDRISC questionnaire. Recruitment will take place through primary healthcare consultations in the Oeiras municipality. Individuals diagnosed with Diabetes Mellitus, those who underwent a diabetes risk assessment more than three years ago, or those with a confirmed diagnosis of diabetes will be excluded. Power calculations and sample size estimation (G-Power, Version 3.1.3) were based on an effect size of 0.2 for the Finnish Diabetes Risk Score (FINDRISC), with α = 0.05 and a power of 0.80. The final sample will consist of 90 participants, accounting for an expected dropout rate of 30%.

Study Design

The "More Health, Less Diabetes" research project is a randomized controlled trial (RCT) with three distinct groups: a control group (CG), an online intervention group (OIG), and an in-person intervention group (IIG). The OIG will receive online educational sessions and structured home-based exercises, while the IIG will participate in in-person educational sessions and supervised physical exercise. The control group will not participate in educational sessions or structured physical exercise.

The intervention will last six months across all groups, with additional follow-up assessments at 12 months. No educational sessions will occur during the follow-up period, and exercise will be optional for all groups. During this phase, control group participants may also join exercise sessions.

Randomization will be automated and conducted by a team member not directly involved in data collection or intervention processes. The Redcap® platform will be used for randomization, ensuring a 1:1:1 allocation ratio stratified by age.

Laboratory Analyses

Biochemical assessments will be conducted through primary healthcare centers. Participants will undergo clinical analyses of glycated hemoglobin (HbA1c) and fasting blood glucose, as well as a 2-hour glucose tolerance test (OGTT) after ingesting 75g of glucose at baseline, after six months, and after one year.

Anthropometric Measurements

Participants' weight and height will be measured with a precision of 0.01 kg and 0.1 cm, respectively, using a scale with an integrated stadiometer (Seca, Hamburg, Germany). Body Mass Index (BMI) will be calculated using the formula [weight (kg)/height² (m²)]. Measurements will be collected at baseline, six months, and one year.

Bioelectrical Impedance Analysis

Whole-body bioelectrical impedance analysis (BIA) will be performed using the AKERN BIA 101/BIVA PRO device, a phase-sensitive single-frequency BIA device. Participants will be instructed to lie down for 10 minutes before measurement. After cleaning the skin, eight low-impedance electrodes (Biatrodes, Akern Srl, Florence, Italy) will be placed on the dorsal surfaces of the feet, ankles, wrists, and hands. This analysis will be performed at baseline, after six months, and after one year.

Dual-Energy X-ray Absorptiometry (DXA)

Lean body mass and fat mass will be determined for the whole body and regionally using dual-energy X-ray absorptiometry (DXA; Hologic Explorer W, QDR for Windows version 12.4, Waltham, MA, USA). This evaluation will be conducted at baseline, after six months, and after one year.

Maximal Cardiopulmonary Exercise Testing

A maximal cardiopulmonary exercise test will be used to assess peak aerobic capacity, peak power output (PPO), and pre-existing cardiac conditions. A ramp incremental protocol will be performed to exhaustion on a cycle ergometer (Monark 839E, Kroons Vag, Sweden). Workload will start at 20 Watts/min and increase in increments of 5-20 Watts/min, based on individual cardiopulmonary responses in the first minute, with a constant cadence of 60 rpm. A cardiologist will monitor all tests using a 12-lead electrocardiogram, and additional data, including heart rate, will be recorded using Omnia software (Cosmed, Rome, Italy). Expired and inspired gases will be continuously analyzed using a Quark RMR w/CPET gas analyzer (version 9.1, Cosmed, Rome, Italy).

Handgrip Strength

The handgrip strength will be accessed using a dynamometer (JAMAR), which measures the upper limb strength and can estimate an individual's total strength.

Vascular Health

Vascular functional health will be measured via pulse wave velocity on the carotid-femoral, carotid-radial, and femoral dorsalis sites (Complior, Alam Medical, France). Structural indices will be assessed via intima-media thickness and arterial stiffness using ultrasonography of the right common carotid artery (Arietta V60, Hitachi Aloka, Japan).

Inclusion Criteria:

1. High or Very High Risk according to the FINDRISC questionnaire;
2. Analytical confirmation of no diagnostic criteria for Diabetes, following a type 2 Diabetes risk assessment;
3. Committed to making lifestyle changes to manage diabetes;
4. Internet access;
5. Availability to participate in the program as required (schedule, location);

Exclusion Criteria:

1. pregnancy (self-report/medical record);
2. Inability to use digital devices
3. Presence of abnormalities on exercise stress test.