Body Composition in Obesity and Metabolic Syndrome

Obesity and Body Composition

Overweight and obesity are growing problems worldwide. In Europe, half of the adults in 2019 were overweight, with 17% classified as obese (CBS, 2024), and the expectation is that these figures will continue to rise. Overweight and obesity are typically expressed in BMI, based on the ratio between total weight and height. But that doesn’t tell the full story. The ratio of fat to muscle mass, as well as the distribution of fat mass, can vary greatly between individuals with the same BMI, including those who are obese.

There is increasing debate about a more precise definition that better reflects potential health risks. At the start of 2025, a group of experts proposed distinguishing between preclinical obesity, where no metabolic dysfunctions are present, and clinical obesity, where such dysfunctions exist (Rubino et al., 2025). To assess individual health, this group recommends measuring fat tissue, or if that’s not possible, combining waist circumference with BMI. Body composition thus plays a role in differentiating between preclinical and clinical obesity.

Obesity and the Metabolic Syndrome

It’s scientifically established that a high BMI is a risk factor for numerous diseases and premature death (Bhaskaran et al., 2018; Di Angelantonio et al., 2016; Whitlock et al., 2009). This is especially true when excess weight is concentrated in the abdominal region, known as "central obesity."

Central obesity, along with insulin resistance, hyperglycemia, low HDL cholesterol, and hypertension, is a criterion for metabolic syndrome. Meeting three out of these five criteria indicates the presence of this syndrome. People with metabolic syndrome have a higher risk of developing type 2 diabetes and cardiovascular diseases. Due to these risks, timely and personalized treatment is essential.

Looking Beyond BMI

In clinical guidelines, a key treatment goal for people with obesity and/or metabolic syndrome is reducing BMI. Based on the robust data linking BMI to disease risk, this approach seems logical. However, as previously noted, BMI says little about an individual’s metabolic status. Moreover, when someone loses weight, they lose not only fat tissue but also muscle tissue. This can have adverse effects, particularly in individuals who already have low and/or declining muscle mass. For example, patients diagnosed with diabetes or heart failure often already have less muscle mass than their healthy peers (Dronkers, 2023).

Less muscle mass also means fewer benefits associated with muscle. For instance, myokines—substances secreted by muscles during contraction—improve insulin sensitivity and counteract the harmful effects of adipokines, signalling proteins secreted by fat tissue (Dronkers, 2023). These reasons underscore the importance of monitoring not only fat mass but also muscle mass.

Muscle Loss with a Calorie-Restricted Diet Without Exercise

People aiming to lose weight often turn to (crash) diets, mainly adjusting their eating habits. While this can be effective for weight reduction, what happens to body composition when weight loss is pursued without increased physical activity?

A systematic review and meta-analysis by Anyiam et al. (2024) investigated this question. They concluded that individuals losing weight on a strict calorie-restricted diet without additional exercise lose 75% fat tissue and 25% muscle tissue. Without adjustments to physical activity, even sarcopenia can become a risk, particularly in older adults.

Preserving Muscle with Combined Interventions

While diet alone can lead to weight loss, more is needed to preserve muscle tissue at least. Several systematic reviews and meta-analyses have examined the effects of different training programs (e.g., cardio, strength training, mixed programs) combined with various diets (e.g., calorie restriction, intermittent fasting, ketogenic diets).

All studies reached the same main conclusion: mixed exercise programs (cardio and strength training) combined with a diet are most effective in achieving weight loss and maintaining or improving favourable body composition (Xie et al., 2024; Eglseer et al., 2023; Batrakoulis et al., 2022)

Monitoring Body Composition: Four Benefits

Professionals guiding individuals in nutrition and lifestyle aim for a personalised approach and positive outcomes. To fully understand the effects and not just focus on BMI, monitoring body composition is essential and beneficial. This provides four key advantages :

• At the start of treatment, a more accurate assessment of the client’s health risks can be made. For example, clients can be informed about the risks of high visceral fat mass.
• These data help determine the composition of the diet, such as total calorie intake and the balance of macronutrients, taking into account any accompanying training plan.
• Based on the data, an appropriate training program can be developed, such as strength versus endurance training.
• Monitoring body composition gives clients better insights into the effects of their efforts. Research shows that physically measuring progress helps achieve goals (Harkin et al., 2016). This can be especially motivating if a client hits a (temporary) weight plateau but sees improvement in fat and lean mass proportions. 

References

Anyiam, O., Abdul Rashid, R. S., Bhatti, A., Khan-Madni, S., Ogunyemi, O., Ardavani, A., & Idris, I. (2024). A Systematic Review and Meta-Analysis of the Effect of Caloric Restriction on Skeletal Muscle Mass in Individuals with, and without, Type 2 Diabetes. Nutrients, 16(19), 3328. https://doi.org/10.3390/nu16193328 

Batrakoulis, A., Jamurtas, A. Z., Metsios, G. S., Perivoliotis, K., Liguori, G., Feito, Y., Riebe, D., Thompson, W. R., Angelopoulos, T. J., Krustrup, P., Mohr, M., Draganidis, D., Poulios, A., & Fatouros, I. G. (2022). Comparative Efficacy of 5 Exercise Types on Cardiometabolic Health in Overweight and Obese Adults: A Systematic Review and Network Meta-Analysis of 81 Randomized Controlled Trials. Circulation. Cardiovascular quality and outcomes, 15(6), e008243. https://doi.org/10.1161/CIRCOUTCOMES.121.008243 

Bhaskaran, K., Dos-Santos-Silva, I., Leon, D. A., Douglas, I. J., & Smeeth, L. (2018). Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3·6 million adults in the UK. The lancet. Diabetes & endocrinology, 6(12), 944–953. https://doi.org/10.1016/S2213-8587(18)30288-2

Centraal Bureau voor de Statistiek. (2024, 3 maart). Obesitas afgelopen 40 jaar verdrievoudigd. Centraal Bureau Voor de Statistiek. https://www.cbs.nl/nl-nl/nieuws/2024/10/obesitas-afgelopen-40-jaar-verdrievoudigd 

Eglseer, D., Traxler, M., Embacher, S., Reiter, L., Schoufour, J. D., Weijs, P. J. M., Voortman, T., Boirie, Y., Cruz-Jentoft, A., Bauer, S., & SO-NUTS consortium (2023). Nutrition and Exercise Interventions to Improve Body Composition for Persons with Overweight or Obesity Near Retirement Age: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials. Advances in nutrition (Bethesda, Md.), 14(3), 516–538. https://doi.org/10.1016/j.advnut.2023.04.001 

Dronkers, J. (2023). Spierfunctie en bewegen. In Soeters et al. (Red.) Leerboek voeding (pp.251-264). Bohn Stafleu van Loghum. https://doi.org/10.1007/978-90-368-2868-0 

Global BMI Mortality Collaboration, Di Angelantonio, E., Bhupathiraju, S.hN., Wormser, D., Gao, P., Kaptoge, S., Berrington de Gonzalez, A., Cairns, B. J., Huxley, R., Jackson, C.hL., Joshy, G., Lewington, S., Manson, J. E., Murphy, N., Patel, A. V., Samet, J. M., Woodward, M., Zheng, W., Zhou, M., Bansal, N., … Hu, F. B. (2016). Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. Lancet (London, England), 388(10046), 776–786. https://doi.org/10.1016/S0140-6736(16)30175-1

Harkin, B., Webb, T. L., Chang, B. P., Prestwich, A., Conner, M., Kellar, I., Benn, Y., & Sheeran, P. (2016). Does monitoring goal progress promote goal attainment? A meta-analysis of the experimental evidence. Psychological bulletin, 142(2), 198–229. https://doi.org/10.1037/bul0000025 

Oh, Y. H., Choi, S., Lee, G., Son, J. S., Kim, K. H., & Park, S. M. (2021). Changes in Body Composition Are Associated with Metabolic Changes and the Risk of Metabolic Syndrome. Journal of clinical medicine, 10(4), 745. https://doi.org/10.3390/jcm10040745 

Prospective Studies Collaboration, Whitlock, G., Lewington, S., Sherliker, P., Clarke, R., Emberson, J., Halsey, J., Qizilbash, N., Collins, R., & Peto, R. (2009). Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet (London, England), 373(9669), 1083–1096. https://doi.org/10.1016/S0140-6736(09)60318-4 

Rubino, F., Cummings, D. E., Eckel, R. H., Cohen, R. V., Wilding, J. P. H., Brown, W. A., Stanford, F. C., Batterham, R. L., Farooqi, I. S., Farpour-Lambert, N. J., Roux, C. W. L., Sattar, N., Baur, L. A., Morrison, K. M., Misra, A., Kadowaki, T., Tham, K. W., Sumithran, P., Garvey, W. T., . . . Mingrone, G. (2025). Definition and diagnostic criteria of clinical obesity. The Lancet Diabetes & Endocrinology. https://doi.org/10.1016/s2213-8587(24)00316-4

Xie, Y., Gu, Y., Li, Z., He, B., & Zhang, L. (2024). Effects of Different Exercises Combined with Different Dietary Interventions on Body Composition: A Systematic Review and Network Meta-Analysis. Nutrients, 16(17), 3007. https://doi.org/10.3390/nu16173007