Obesity has become a major public health concern worldwide. According to the OECD, 54% of people over the age of 15 were overweight or obese in 2023. The widespread availability of highly processed, energy dense foods, chronic stress exposure, and increasingly sedentary lifestyles are among the primary contributors to rising obesity rates.
Obesity is commonly defined as a condition characterized by excess body fat and is typically assessed using body mass index (BMI) or waist circumference measurements. A BMI between 25 and 29.9 kg/m² is classified as overweight, while a BMI of 30 kg/m² or higher is classified as obesity. Obesity rarely exists in isolation and is associated with a wide range of adverse health outcomes, including type 2 diabetes, cardiovascular disease, reduced mobility, musculoskeletal disorders, and certain cancers. As obesity prevalence continues to rise, the burden of these associated chronic conditions is expected to increase accordingly.
Table of Contents
How Much Does Obesity Increase Diabetes Risk?
The relationship between obesity and type 2 diabetes is one of the strongest and most well-established relationships in metabolic health research. Obesity is recognized as the most significant modifiable risk factor for the development of type 2 diabetes. Research consistently shows that the majority of individuals living with type 2 diabetes are also living with overweight or obesity. This strong association has led to the term “diabesity” being used to describe the frequent coexistence of obesity and diabetes.
There are two types of diabetes – type 1 and type 2. A 2015 study found that 10% if Irish adults over 50 have diabetes, with being obese and having low physical activity levels being associated risk factors of developing type 2 diabetes.
Type 2 diabetes is the most common form of the disease in the United States and represents a major global chronic health burden. While type 1 diabetes typically presents in childhood, type 2 diabetes has traditionally affected adults. However, it is increasingly being diagnosed in children and adolescents in many Western countries.
Research has shown that a BMI above a healthy range substantially increases the risk of type 2 diabetes. The global rise in obesity prevalence has closely mirrored the increasing incidence of diabetes. Importantly, obesity alone does not guarantee the development of diabetes. Instead, it acts as a risk factor that interacts with genetics, diet quality, physical activity levels, and environmental influences.
The Physiology Behind the Link: Why Excess Fat Promotes Diabetes
Insulin Resistance: What Obesity Does to Your Cells
Excess fat, particularly around the abdominal area, plays a significant role in the development of insulin resistance. Insulin is an important hormone that allows glucose to move from the bloodstream into cells, where it is used for energy. When insulin resistance develops, tissues such as muscle, liver, and fat cells become less responsive to insulin, causing glucose to remain in the bloodstream and blood sugar levels to rise.
In individuals with obesity, excess adipose tissue releases elevated levels of free fatty acids and pro-inflammatory molecules into the bloodstream. These substances interfere with insulin signaling and reduce the ability of insulin receptors on muscle, liver, and fat cells to function properly. Over time, chronic, low-grade inflammation further reduces insulin sensitivity, while changes in hormones and adipokines produced by fat tissue disrupt normal glucose metabolism. As muscle tissue becomes less responsive to insulin, it takes up less glucose from the blood, reinforcing a cycle of insulin resistance.
Beta-Cell Stress and Pancreatic Response
As insulin resistance progresses, the pancreas compensates by increasing insulin production to maintain normal blood glucose levels. In the early stages of insulin resistance and prediabetes, this increased insulin output may temporarily keep blood glucose within a healthy range. However, sustained insulin demand places significant stress on pancreatic beta cells, which are responsible for insulin production.
Over time, this chronic stress and demand can impair the beta-cell function and reduce their ability to secrete insulin. When the pancreas can no longer meet the body’s insulin requirements, blood glucose levels rise persistently, contributing to the development of type 2 diabetes.
Why Abdominal/Visceral Fat is Particularly Risky
Not all body fat has the same metabolic impact. Abdominal fat, particularly visceral fat stored deep around the organs, is especially strongly associated with diabetes risk. Subcutaneous fat stored beneath the skin behaves differently from visceral fat, which is highly metabolically active. Visceral fat releases higher levels of inflammatory substances and fatty acids directly into the blood stream. Its proximity to key metabolic organs allows visceral fat to effectively disrupt insulin sensitivity and glucose regulation. This ultimately can increase the risk of type 2 diabetes even in people who may not appear significantly overweight. Elevated insulin levels can also promote further fat storage, creating a feedback loop that makes weight loss more challenging for individuals with insulin resistance or diabetes.
Other Contributing Physiological Processes
Insulin resistance not only raises blood glucose levels but also disrupts normal appetite regulation and hunger signalling. When the body is unable to use glucose efficiently for energy, it behaves as though it is in an energy deficit. This can increase hunger cues and cravings while promoting fat storage. This is why many individuals living with diabetes find appetite control and weight management particularly difficult.
Beyond insulin resistance and pancreatic strain, obesity affects the body in many interconnected pathways. Excess body fat fuels chronic, low-grade inflammation, which negatively impacts metabolic health and increases susceptibility to other chronic conditions. Carrying extra weight can also make movement more difficult. This can reduce mobility and physical activity over time, while placing added stress on bones and joints. Together, these factors help explain why weight loss through diet and exercise alone can be particularly challenging for individuals with insulin resistance or diabetes.
Does Obesity Always Cause Diabetes?
Genetic & Environmental Influences
Individuals living with obesity are around six times more likely to develop diabetes than those at a healthy weight. Obesity is undoubtedly one of the greatest driving factors of diabetes. Although genetic and environmental factors also play a role, factors such as family history, high stress, an unhealthy diet, sedentary lifestyle, and poor gut health can also increase the risk of developing diabetes.
The “Metabolically Healthy Obese” Phenomenon
Obesity doesn’t always cause metabolic abnormalities. In some cases, individuals with obesity might have a better tolerance to glucose and produce sufficient insulin to combat blood sugar, without putting stress on the pancreas. The ‘metabolic healthy obese’ phenomenon is where an individual has a BMI over 30 but lacks the presence of abnormalities such as high blood pressure, cardiovascular disease, type 2 diabetes, and high cholesterol. The reason why some individuals may experience abnormalities and others don’t is influenced by factors such as genetics, lower levels of inflammation, metabolism, and differences in fat distribution.
Evidence suggests that metabolically healthy obesity may represent a temporary state, with many individuals developing metabolic abnormalities over time. suggests that metabolically healthy obesity may represent a temporary state, with many individuals developing metabolic abnormalities over time.
Other Risk Factors That Compound the Obesity–Diabetes Link
Lifestyle factors such as chronic stress, poor sleep, unhealthy diets, and low physical activity all play a role in increasing risk of developing diabetes. Many of these factors are often overlooked, yet even small changes, like getting enough sleep, can improve how the body responds to insulin and help lower the risk of developing diabetes.
People with obesity often have lower levels of adiponectin, which helps improve insulin sensitivity, and often develop resistance to leptin, a hormone that regulates appetite. These hormonal changes, combined with genetic risk and lifestyle factors, impair regulation of blood sugar and can increase the likelihood of type 2 diabetes.
Can Risk Be Reversed? Evidence for Prevention, Weight Loss & Lifestyle Change
Weight Loss, Fat Reduction & Improved Insulin Sensitivity
Weight loss can potentially reverse the effects of insulin resistance and induce remission in some individuals. It can improve glycaemic control by increasing insulin sensitivity in the early stages. Lifestyle interventions such as incorporating a healthy diet that supports weight loss, regular exercise, sleep hygiene and reducing stress can promote a healthy weight while also helping to manage diabetes symptoms. Losing just 5% to 10% of overall body weight can have a significant effect on improving type 2 diabetes.
Lifestyle Interventions: Diet, Physical Activity, Sleep, Stress Management
Lifestyle interventions and small changes to daily habits can go a long way in reducing risk factors of developing both diabetes and obesity. Reviewing your diet can help you spot unhealthy eating habits. You can improve it by controlling portion sizes, choosing more whole foods, and eating more fruit and vegetables.
Increasing daily movement by even a brisk walk after eating a meal has been found to have a positive effect on reducing blood sugar spikes. Exercise in general can promote the body’s ability to use insulin effectively and decrease insulin resistance.
Sleep and stress management also play a vital role in managing blood glucose. When the body is under stress, its ability to deal with glucose spikes is compromised. To combat this, aiming for around seven to nine hours of sleep is recommended. Managing stress through daily movement, time in nature, or deep breathing techniques can also be beneficial. Lifestyle interventions are most effective when implemented together and sustained over time.
Myths, Misconceptions & Common Questions
1. “Diabetes only affects overweight people.”
False. While overweight and obesity greatly increase risk, diabetes can (and does) occur in people who are not overweight. Genetics, age, ethnicity, fat distribution, and lifestyle all influence risk.
2. “Obesity always causes diabetes” – True or false?
False. Obesity increases the probability of developing diabetes but doesn’t guarantee it. Many people with obesity remain metabolically healthy.
3. “Only BMI matters.”
False. BMI is only a rough estimate of overweight or obesity. How and where fat is stored, whether it’s visceral or subcutaneous, and how metabolically active it is, is a much better indicator.
Frequently Asked Questions:
1. Can you have diabetes without being overweight?
Yes, although being overweight does increase the risk of diabetes, not everyone that is overweight will develop diabetes. Other factors such as genetics, ethnicity, fat distribution, and age can promote the onset of diabetes, regardless of whether the individual is obese.
2. Is all body fat equally harmful for diabetes risk?
No, fat that is stored viscerally (around organs) or ectopically (in stomach or liver) behaves differently to subcutaneous fat (under the skin) and promotes insulin resistance. Visceral fat is more metabolically active and inflammatory than subcutaneous fat, making an excess of visceral fat a concern for metabolic health.
3. Can losing weight reverse insulin resistance?
Yes, reducing total body fat percentage, especially visceral fat, can restore insulin sensitivity, ease pancreatic stress, and improve metabolic markers.
4. How much weight do I need to lose to lower my diabetes risk?
Even a small step towards a healthier weight can make a huge difference! Research suggests that even a reduction of 5% in body weight can significantly improve insulin sensitivity.
5. What role does visceral fat play in diabetes risk?
Visceral fat is a major driver of insulin resistance, inflammation, and metabolic dysfunction. It is a typically stronger indicator of an individual’s diabetes risk more than total body fat.
6. Can improving sleep reduce diabetes risk?
Yes. Links have been discovered in the relationship between poor sleep and increased diabetes risks. Habits such as late night snacking, and poor sleep during adolescence increases one’s risk of obesity and therefore puts them at greater risk of diabetes. Adequate sleep is necessary for our metabolic system and regulating our hunger cues.
7. Is diabetes caused only by sugar intake?
No, Although excessive sugar and refined carbohydrate consumption contribute to the onset of diabetes, the disease is multifactorial. The manifestation of diabetes may involve fat distribution, insulin resistance, inflammation, genetics, physical activity, and overall lifestyle.
Conclusion
The link between obesity and type 2 diabetes is complex, but clear. A high body mass index and excess body fat, particularly around the stomach can disrupt how the body uses insulin. As a result, a strain is placed on the pancreas and overtime, and its ability to manage blood glucose levels is impacted.
It is important to remember that having one risk factor does not mean that you will inevitably become diabetic. Some risk factors such as family history and genetic disposition are beyond our control. What’s important is striving to make small changes that can lead to an overall healthier lifestyle. These changes can be as simple as adding more whole foods to the diet, or managing stress, increasing daily movement, and getting more sleep can significantly improve insulin sensitivity and metabolic health. Research consistently shows that modest weight loss and lifestyle changes can reduce diabetes risk and, in some cases, even reverse early metabolic changes.
For those living with obesity or type 2 diabetes, progress does not have to be all-or-nothing. There is no single “perfect” solution, and quick fixes rarely lead to long-term success. Instead, focusing on gradual, realistic habits and seeking medical support when needed is key. For some, a simple lifestyle change may be needed, for others, therapeutic options can lead to significant improvements.
Here at Atlantia, we believe prevention is better than cure. Knowing how obesity and diabetes are linked is the first step. With the right support and steady, manageable changes, better metabolic health is within reach.
co-authored by – Chloe McDonough