A total of 1,811 records were identified through the electronic searches. Of these, 97 were deemed eligible and were assessed for study abstract. Articles were removed because they were case studies or did not include a sarcopenic obesity sample (n = 58), sarcopenic obesity was not the primary reported results of an intervention (n = 18), the articles were reviews or study design did not fit inclusion criteria (n = 10), and wrong intervention setting (n = 7). Additional one article was added from a hand searched method. Thus, a total of 7 trials were analysed in this scoping review. A flow diagram of the study selection procedure is shown in Fig. 1.

Fig. 1

Flow chart of scoping review

Characteristics of included articles

Among the 7 included studies, none of the studies recruited both sexes, three studies recruited male subjects [36, 39, 40] while four studies recruited female as subjects [37, 38, 41, 42]. The sample size ranged from 16 to 139 subjects. Four out of six studies assessed the effectiveness of protein supplementation with combination of exercise training [36,37,38,39, 41]. One study evaluated the whole-body electromyostimulation and protein supplementation [40], while another study prescribed low calorie diet with protein supplementation to determine its effects on sarcopenic obesity [42]. Of these, six studies were randomised controlled trials [36,37,38,39,40,41] and one was a pre-post study design [42]. The majority (26%) of the studies was reported from Italy [38, 42] and German [39, 40], one from Canada [36], one from Japan [37], and one from Brazil [41]. The characteristics of the included studies have been summarized in Table 3.

Table 3 Characteristics & outcomes of included articles Definition of sarcopenic obesity

In view of the definition of sarcopenia, different studies used different sarcopenia diagnoses. Skeletal muscle mass (Appendicular skeletal mass, ASM), lean body mass, ideal fat free mass, and skeletal muscle mass index were commonly used in most studies to determine sarcopenic condition [36,37,38, 41]. Three studies mentioned the used of the EWGSOP (European Working Group on Sarcopenia in Older People) as diagnostic criteria for sarcopenia in older adults [39, 40, 42]. In terms of obesity, the body fat percentage used was ranged between 27 and 38% [37,38,39,40,41,42]. Only one study that used body mass index (BMI) > 30 kg/m2 to determine the weight status of the subjects [36].

Types of protein supplementation & protein intake

These studies included interventions of protein supplementation (Leucine enriched essential amino acid, EAA; whey protein) [36,37,38,39,40,41,42]. In one study, participants underwent a 3-month intervention involving the combination of catechin and a protein supplement [37]. The protein intake prescription by these studies ranged from 1.0 to 1.8 g/kg/BW/day for intervention group, for control group the protein intake was typically between 0.8 and 1.0 g/kg/BW/day [36, 38,39,40,41,42].

Effects of different interventions on sarcopenic obesity

The effectiveness of the intervention in older adults was assessed through various sarcopenia evaluations. The most used sarcopenia measurement was lean muscle mass [36, 38] muscle strength [38, 42] handgrip strength [39, 42]. Measurement of body fat mass was seen in majority of the studies [36, 37, 39, 42]. In addition, body weight [36, 38], body trunk fat [36, 40, 42], and waist circumference [40, 42], were also measured to determine the effects on obesity.

The included intervention studies have consistently shown that exercise combined with protein supplement interventions, can lead to significant improvements in sarcopenic conditions such as muscle mass, strength, and physical function. Two studies utilised resistance training exercise in the intervention [36, 41], while one study combined both resistance exercise and aerobic exercise in the intervention [37]. The duration of exercise performed ranged from 2 to 3 times per week, with each session lasting 1 h [36, 37, 41]. However, one article did not report the duration of the exercise [36]. The exercise training also demonstrated a significant weight loss, loss of fat mass or trunk mass while preserving the lean muscle mass [36, 37, 41]. The results are the same as the intervention studies that utilised electromyostimulation (EMS) as an alternative to exercise [39]. Protein supplementation alone also showed improvement in sarcopenia measurements [38, 39, 42] as well as decrease in fat mass [36, 37], weight status [28], and waist circumference [42].

Effects of interventions on metabolic and inflammatory biomarkers

Five studies examined the effects of intervention on metabolic and inflammatory biomarkers such as total cholesterol (CHOL), triglycerides (TG), low density lipoprotein, high density lipoprotein (HDL), C-reactive protein (CRP), and Interleukin-6 (IL-6) on the subjects [36,