Drawing on data from the Geelong Osteoporosis Study, Population Health researchers have investigated a range of unexpected consequences of obesity, highlighting opportunities to inform clinical practice, public health awareness campaigns, and ongoing clinical trials.
Obesity rates in Australia on the rise
According to the Australia Institute of Health and Welfare, 32 per cent of adults aged 18 and over were living with obesity in 2022 – an increase from 19 per cent in 1995.
Obesity is defined as abnormal or excessive fat accumulation that can impair health. Over time, it has presented itself as a complex chronic disease, and a risk factor for other types of disorders.
Getting a picture of obesity through the Geelong Osteoporosis Study
The Deakin University-led Geelong Osteoporosis Study (GOS) is one of only a few large population-based cohort studies in Australia documenting changes to the health and wellbeing of young, middle-aged, and older women and men over the decades.
Initially designed to focus on osteoporosis and bone health, the study has grown to include data related to the onset and progression of a variety of disorders.
In 2024, it notched up 30 years of data collection that is helping build a better understanding of how our bodies age.
According to Population Health theme leader Professor Julie Pasco, the data provided an important opportunity to understand the impacts of obesity in the population and the risk factors it presents for other types of disorders.
Understanding the impacts of obesity on mental and physical health
The research into obesity, led by Prof Pasco, has revealed a number of unexpected consequences of the metabolic disorder, and helped give a better understanding of some of its more widely known impacts. Some of the findings are detailed as follows:
Ageing: Obesity can be considered a phenotype of premature ageing. The data show that body composition, the proportions of fat, bone, and muscle in the body, change during ageing, even if body weight remains apparently stable.
Fatty liver and fatty muscle: Our research confirmed that obesity increases the risk of fat building up in body organs and identified the co-existence of fat accumulation in the liver (fatty liver) and muscles (fatty muscle). Not only does this impact glucose control, it can also lead to metabolic dysfunction-associated steatotic liver disease (MASLD) and muscle weakness.
Mild obesity-related diabetes (MOD): Recent research has shone a light on five new subgroups of diabetes, namely: severe insulin-resistant diabetes (SIRD), severe insulin-deficient diabetes (SIDD), severe autoimmune diabetes (SAID), mild age-related diabetes (MARD), and mild obesity-related diabetes (MOD).
Accounting for 24 per cent of participants with diabetes, the MOD subgroup had the highest BMI (by definition) and mean diastolic blood pressure, and the second highest prevalence of poor renal function (behind MARD). Obesity is a known risk factor in the progression of cardiovascular disease and cancer. As diabetes increases the risk of cardiovascular complications, the MOD subgroup has the potential to be at high risk of these complications.
Falls: The data reports that men and women with greater BMI are more likely to sustain a fall. Obesity-related contributing factors include impaired balance, muscle weakness, sarcopenic obesity, polypharmacy, and an increased number of comorbid conditions.
Fractures: Prof Pasco said the team’s involvement in a large international meta-analysis contributed to a pooled dataset comprising 1.7 million adults from 32 countries and confirmed that being underweight conferred the greatest risk for fracture, while overweight and obesity were protective.
“After accounting for differences in bone mass, however, obesity was revealed as a risk factor for fracture, and this was more marked in men compared to women. Sex-specific hormonal differences affecting muscles, bones, and body fat distribution are likely contributors to this finding,” she explained.
Back pain: A collaboration with researchers from Monash University used GOS data to show that men who had weight gain of as little as 3kg over a five-year period were more likely to have back pain and suffer long-term disability. The prevalence of back pain among men of working age is high in Australia and afflicted men tend to take prolonged time off work.
Negative emotions: The team observed that participants with obesity had greater negative affect scores on the Positive and Negative Affect Schedule, reflecting emotions such as distress, anger, disgust, fear, and shame.
While this association was partly explained by physical illness, other drivers likely include stigma, social disadvantage, poor self-esteem, and perceived lower levels of social integration and support due to obesity.
Depression: While it is known that obesity is often comorbid with and bidirectionally linked to depression, not all individuals with obesity develop depression. By measuring systemic levels of the inflammatory marker, high-sensitivity CRP, the research team determined that women with obesity and high levels of inflammation are at increased risk of subsequent major depression.
Paradoxical nutritional deficiency: The data showed no apparent pattern between categories of BMI (underweight, normal weight, overweight, obesity) and energy intake.
Regardless of adequate energy intake, diets in all BMI categories were low in zinc, calcium, folate, and fibre. Such shortcomings suggest that nutrient-dense foods (such as whole grains and vegetables, particularly leafy green vegetables) are under-consumed, while processed foods with high saturated fat and salt content are consumed excessively.
“These observations underscore the importance of recognising the nutrient density of foods so that nutrition is not compromised when energy intakes are restricted. This is relevant for weight-loss programs, particularly for older individuals, where muscle mass and bone mass should be preserved,” Prof Pasco said.
Finding present opportunities for improved obesity support and prevention
Prof Pasco said the data and related analyses can be used to introduce a range of factors to improve healthy ageing and the management of chronic diseases.
“In the case of the link between obesity and depression, for example, we can provide this information to medical
practitioners who can then be on the lookout for depression in someone with obesity. So this information alerts practitioners to the other problems that could exist with a diagnosis of obesity.”
“Overall, the observations can also be used to inform the design of clinical trials, improve public health campaigns, and assist economic modelling when it comes to obesity in the population.”
This article was published in our 2024 Annual Report. Looking for more? Check it out here.
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