Sarcopenic obesity, characterised by concurrent reduced muscle mass and excess body fat, affects 11% of older adults worldwide, rising to 23% in those over 75. Considering the negative synergistic impact on health, promoting muscle mass gains while reducing fat mass remains a significant challenge, necessitating urgent and effective intervention strategies for managing SO. Exercise and nutrition are the primary interventions recommended for SO.

This project aims to evaluate the effects of the EatWellLog App developed by the investigators' team for local older adults, in improving:

• their sarcopenic obesity status, measured by all four diagnostic criteria, including grip strength, muscle mass, physical performance and body fat mass (primary outcome), and,
• nutritional self-efficacy, nutritional status, dietary quality, health-related quality of life, and adherence to diet and exercise regimens (secondary outcomes), by enhancing the self-management abilities and longer-term adherence to daily diet management among participants in the M-health group using the App, compared to the control group.

The EatWellLog App, designed for older adults with SO, incorporating Klasnja and Pratt's five-strategy framework for mobile health (mHealth) applications development to facilitate health behavioural change. This App supports users with SO in managing daily diets that promote gradual weight loss and muscle mass preservation, adhering to the dietary regimen for this population.

Forty older adults with SO will be recruited from local community health centres and then randomized to either m-health or control groups. Both groups will receive an 8-week supervised programme separately. The programme consists of personalised dietary modification programme and group-based exercise training which have been tested and used in the investigators' pilot and General Research Fund (GRF) project. Additionally, only the m-health group will be instructed to use the App for daily diet self-management.

Participants will be assessed on a variety of outcomes immediately after the 8-week supervised programme (T1), which will be compared to the baseline (T0). To explore the possible long-term effects of the intervention, other measurements will be conducted at 3-(T2) and 6-(T3) months after the supervised programme, which will be compared with those conducted at T0.

Sarcopenic obesity (SO), characterized by concurrent reduced muscle mass and excess body fat, affects 11% older adults worldwide, rising to 23% among those over 751. Older adults with reduced muscle mass are 1.95-2.62 times prone to obesity than those with normal muscle mass. This is due to shared etiological factors between sarcopenia and obesity such as sedentary habits and aging-related biological shifts, including decreased anabolic hormones, increased insulin resistance, and escalated oxidative stress. The combination of sarcopenia and obesity has a compounding negative impact on health, raising the likelihood of knee and hip osteoarthritis, which leads to reduced physical capabilities, as well as increasing the risk of cardio-metabolic diseases, institutionalized, and death, exceeding the risks of sarcopenia or obesity alone.

Addressing SO effectively to promote muscle mass gains while reducing fat mass remains a significant challenge, necessitating urgent and effective intervention strategies. Currently, exercise and nutrition interventions, are the most commonly recommended interventions.

Exercise and Nutrition Interventions for SO A recent systematic review of 11 trials with 440 SO participants showed that resistance training twice weekly for 20 minutes over a minimum of 8 weeks effectively enhances body composition, muscle strength, and gait speed. Furthermore, evidence suggested that combining aerobic and resistance training with increased protein intake is more effective in reducing body fat than resistance training alone but had no effects on muscle mass and strength. Another systematic review of eight trials with 605 SO participants found that resistance training alone could increase muscle strength. To also improve physical functions (i.e., gait speed and grip strength), exercise combining aerobic and resistance training with dietary supplements seems to have more promising results. The findings in a recent umbrella review of meta-analyses concluded that exercise interventions (either resistance training or combined resistance and aerobic exercise) are beneficial for body composition and physical performance in older adults with SO. However, the added value of exercise with nutrition interventions (either protein supplement and dietary modifications) produces inconsistent results.

Adequate protein intake is vital for muscle building, and calorie restriction is effective at reducing fat mass. Thus, nutrition is a critical factor in the onset and progression of SO, although the evidence for nutrition interventions in reserving SO demonstrated inconsistent effects, especially regarding muscle mass and strength. When implementing a weight loss diet for individuals with SO, it is important to balance fat reduction with muscle mass preservation by ensure adequate protein intake to prevent exacerbating muscle loss. Evidence suggests that the source of protein is crucial for muscle retention, specifically for animal-based proteins, which are high in leucine, may be more effective in preserving muscle mass during weight loss and in maintaining physical function. While nutritional supplements are commonly used to increase protein intake, their effects on SO remain inconsistent and may cause side effects such as digestive issues, interact with certain medications, dehydration, liver and renal damage, bloating, and calcium loss. The investigators advocates for an unhealthy diet incorporating a full spectrum of nutrients from whole foods, in line with the Dietary Guidelines for Americans, 2020-2025, as the preferred approach over supplements for those with sarcopenic obesity. Modifying daily dietary habits of individuals with SO may provide more sustainable benefits than merely adding supplements to their diet.

A recent systematic review examining nutrition interventions in managing sarcopenic obesity analysed nine studies but only two assessed the impact of dietary modifications on protein intake among older adults with SO. The first randomized controlled trial (RCT) assessed the impact of a low-calorie diet with normal (0.8 g/kg body weight/day) versus high protein intake (1.2 g/kg body weight/day) over three months in 104 older women with SO. The study found muscle mass decreased in the normal protein group concurrent with fat loss, while the high protein group saw muscle mass preservation. The second pilot RCT involving 18 women compared a low-calorie diet with placebo to one with high protein (1.2-1.4 g/kg body weight/day) over four months. Significant muscle strength gains were noted in the high protein group, though changes in muscle mass were not significantly different between the two groups. While the findings in these two trials provided preliminary evidence that hypocaloric diet and high protein intake may be necessary for managing SO, particularly for preserving mass muscle and strength. These studies, however, had limitations such as broad inclusion criteria for sarcopenic obesity, lacking a standardized diagnostic protocol, insufficient data on dietary adherence, and opaque details regarding randomization and intervention specifics. More rigorous research is needed to investigate the impact of diet modification on sarcopenic obesity.

Conventional dietary modification intervention that relies on face-to-face consultation and monitoring, faced lots of challenges which included participants' poor compliance to the recommended dietary regimen, high attrition, time constraints and manpower. Those were major threats to the viability of the study leading to inconsistent treatment effects. In addition, the therapeutic effect may gradually reduces after the completion of the dietary training program. Additionally, the therapeutic effect may gradually reduce after the completion of the dietary program.

Rationale for developing a m-health based intervention for SO Systematic reviews found that m-health dietary intervention, with appropriate behaviour change techniques, can achieve dietary behaviour change across a range of chronic illnesses, such as obesity, metabolic syndrome, cardiovascular disease with relatively low attrition rates. To the best of the knowledge, there are no studies evaluating the effects of m-health dietary interventions on SO. The success of m-health interventions in other chronic conditions could potentially be adapted to improve health behaviors in patients with SO.

Aims and Hypotheses to be Tested.

The study aims to evaluate the effects of the EatWellLog App (hereafter referred to as "the App"), designed by the investigators' team to address the needs of local older adults, in improving:

• their sarcopenic obesity status, measured by all four diagnostic criteria, including grip strength, muscle mass, physical performance and body fat mass (primary outcome), and,
• nutritional self-efficacy, nutritional status, dietary quality, health-related quality of life, and adherence to diet and exercise regimens (secondary outcomes), by enhancing the self-management abilities and longer-term adherence to daily diet management among participants in the M-health group using the App, compared to the control group.

It is hypothesised that the App users will demonstrate significant and sustained improvements in SO status and secondary outcomes immediately after the supervised nutrition and exercise programme and at 3-and 6-month follow ups, compared to the control group who receive the same supervised programme without the App.

The investigators will also explore users' experience with the App by focus groups with all participants in the M-health group, 6-8 per group, to understand their experience of using the App. Additionally, the investigators will analyse the App usage data including session duration, frequency, feature utilisation, and retention rates, at the 3-month and 6-month follow-ups.

Inclusion Criteria:

• Aged 65 or above, and living in the community;

• Having SO according to the Asian Working Group for Sarcopenia (AWGS) and the World Health Organization (WHO)'s obesity criteria for Asians:

  1. Early-stage sarcopenia indicated by fulfilment of one of the following criteria; handgrip strength <28 kg (men) and <18 kg (women); appendicular skeletal muscle mass (ASM)/ height2 <7 kg/m2 (men) and <5.7 kg/m2 (women), or SPPB score of <9; Short Physical Performance Battery (SPPB) score of <9,
  2. Obesity indicated by BMI ≥25 kg/m2, waist circumference ≥90 cm (men) and ≥80 cm (women), or body fat >30%;

• Own a smartphone with internet access; and

• Proficiency in communicating, reading, and writing in Chinese, and without major hearing and vision impairments to ensure that comprehension of our instructions.

Exclusion Criteria:

• Individuals with diseases impacting digestion or food consumption, including severe cardiac/ pulmonary/ renal diseases, diabetes, cancer, or autoimmune disorders;
• Those on medications affecting eating habits, digestion, or metabolism, such as weight loss drugs;
• Persons with alcohol use disorder as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), potentially hindering dietary behaviour changes;
• Those with medical implants like pacemakers that could be disrupted by the bioelectric impedance analysis (BIA's) low-level electrical currents.

For confidentiality, the data will be kept anonymous and the information of all participants will be replaced by reference codes. The data collected will be kept in a locked place and electronic versions will be encrypted, and only be accessible by the researchers. All data will be destroyed within 7 years after the completion of this research.

An independent assessor who is blinded to the group allocations will assess the participants' outcomes.