How Sugar Damages Your Body: From Insulin Resistance to Chronic Pain
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By Dr. Jeffrey Peng, MD · Published March 4, 2026 · 8 min read
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Sugar is everywhere — and who does not enjoy a little sweetness? But the reality is that sugar poses a silent threat to health, contributing to worse outcomes and chronic pain regardless of body weight. Whether you are normal weight, overweight, or lean, excess sugar is toxic to the body. In this article, I will break down the hidden ways sugar affects your health and how reducing your intake can make a meaningful difference.
According to the American Heart Association, adults consume an average of 17 teaspoons of added sugar per day — more than double the recommended amount. That adds up to roughly 60 pounds of added sugar per person each year.
How Does Excess Sugar Lead to Insulin Resistance?
Consuming too much sugar can lead to insulin resistance, a precursor to type 2 diabetes. Insulin is a hormone produced by the pancreas that regulates blood sugar levels. When the cells in your muscles, fat, and liver become less responsive to insulin, the pancreas compensates by producing more of it. Initially, this keeps blood sugar levels stable.
However, if high sugar intake persists, the pancreas eventually struggles to keep up. Blood sugar levels begin to rise, leading first to prediabetes and potentially to full-blown diabetes. These metabolic changes affect every system in your body — from your immune defenses to your cardiovascular system to your joints and tendons.
Does Sugar Suppress the Immune System?
Yes. Research demonstrates that after consuming sugar, the efficiency of white blood cells in attacking bacteria is significantly reduced, leading to a weakened immune response (Shomali et al., 2020, Biotechnology and Applied Biochemistry). This is one reason why individuals with diabetes face a significantly higher risk of respiratory infections such as influenza and pneumonia, urinary tract infections, and skin infections.
Can Sugar Cause Heart Disease?
Diets high in sugar contribute to atherosclerosis, which is an underlying cause of heart disease. Elevated blood sugar levels promote the formation of advanced glycation end products (AGEs), which cause plaque buildup in blood vessels. In addition, high sugar levels trigger chronic inflammation and damage the endothelial cells lining blood vessel walls — both of which accelerate cardiovascular disease and increase heart attack risk.
How Does Sugar Increase Pain and Inflammation?
Chronic inflammation is the mechanism through which elevated blood sugar levels affect how we experience pain. High blood sugar has been linked to the promotion of proinflammatory cytokines — signaling molecules involved in both inflammatory pain and nerve pain (Sommer & Kress, 2004, Neuroscience Letters).
A large Danish population study found that individuals with diabetes had significantly elevated odds of musculoskeletal pain, osteoarthritis, osteoporosis, and rheumatoid arthritis compared to those without diabetes (Rehling et al., 2019, Journal of Diabetes Research). In my practice, this pattern is consistent: sugar in the body causes low-grade inflammation that increases stress on tissues and accelerates the degeneration of joints and soft tissue.
Are People with High Blood Sugar at Greater Risk for Tendon Injuries?
The risk is substantial. A prospective study from the Copenhagen City Heart Study reported that individuals with prediabetes and diabetes had a roughly three times higher risk of tendon injury in the lower extremities compared to those with normal blood sugar levels. Those with metabolic syndrome faced approximately 2.5 times higher risk in both the upper and lower extremities (Skovgaard et al., 2021, Scandinavian Journal of Medicine & Science in Sports).
Does Metabolic Syndrome Affect Treatment Outcomes?
Unfortunately, yes. Research shows that individuals with metabolic syndrome are not only more likely to experience musculoskeletal pain, but they also respond less favorably to standard treatments. In a matched case-control study of trigger finger patients, those with metabolic syndrome had a 49% treatment failure rate with corticosteroid injections compared to only 19% in the control group (Roh et al., 2016, The Journal of Hand Surgery). They also require longer courses of treatments including physical therapy, pain medications, or injections.
Are All Sugars Equally Harmful?
No — and this is an important distinction. Almost all of the negative health effects described above result from added sugars, processed carbohydrates, and simple sugars. Many of these effects do not apply to complex carbohydrates.
Simple sugars — including glucose, fructose, and sucrose — are found in refined foods such as white bread, pasta, white rice, and potatoes. These sugars are rapidly digested and absorbed, leading to quick spikes in blood sugar. Occasional spikes are manageable, but repeated spikes throughout the day can overwhelm the body's ability to regulate blood sugar, potentially leading to insulin resistance over time.
Complex carbohydrates, on the other hand, are found in whole foods such as fruits, vegetables, legumes, and whole grains. These foods contain fiber that slows digestion, resulting in a more gradual rise in blood sugar. This helps the body manage energy more efficiently and prevents the inflammatory response associated with sugar spikes. These foods are also rich in nutrients, phytochemicals, and antioxidants that support overall health.
In fact, a large prospective cohort study found that replacing processed grains and starchy vegetables with whole grains, fruits, and non-starchy vegetables was associated with improved weight outcomes (Liu et al., 2023, JAMA Network Open).
How Can You Reduce Your Sugar Intake?
When reducing sugar intake, the goal is to maintain complex carbohydrates while decreasing simple and added sugars. The easiest place to start is your beverages. According to the American Heart Association, beverages account for 47% of all added sugar consumption — with soft drinks alone comprising 25%, followed by fruit drinks at 11%, coffee and tea at 7%, and sports and energy drinks at 3%.
Start gradually. If you regularly drink sugary beverages, begin by mixing them with water — starting with a 50/50 ratio and increasing the water proportion over time. Eventually, make water your default drink. If plain water does not appeal to you, try adding slices of fruit such as lemon, lime, cucumber, or berries for natural flavor.
The second-largest category is snacks and sweets, comprising 31% of all added sugars. Together with beverages, these two categories account for nearly 80% of added sugar intake. Here is what I recommend to my patients:
Read food labels carefully. Check ingredient lists for sugars such as sucrose or high-fructose corn syrup. Opt for natural spices that provide flavor, such as cinnamon or vanilla. Consider keto-friendly snacks that are lower in carbohydrates and higher in healthy fats and proteins — examples include cheese, nuts, and seeds.
Finding a Sustainable Approach to Reducing Sugar
Sugar can be quite addictive. It activates the same reward pathways in the brain as other addictive substances, generating cravings and a temporary sense of well-being. When we are stressed, this cycle intensifies — we reach for sugar to regulate mood, appetite, and pain perception, but the relief is short-lived.
The most important principle I emphasize with my patients is balance. You do not need an extremely restrictive diet. Aiming for a perfect "A+ diet" may yield quick results, but those results only last if the diet is sustainable. In my experience, it is far more effective to adopt a realistic and manageable dietary plan. An achievable "B diet" that fits your lifestyle is always better than an "A+ diet" that is too restrictive to maintain. The goal is to avoid the "F diet" that caused the health problems in the first place.
If you are concerned about how your diet may be affecting your joint pain or overall health, consider scheduling a consultation to discuss a personalized plan.
References
1. Shomali N, Mahmoudi J, Mahmoodpoor A, et al. Harmful effects of high amounts of glucose on the immune system: An updated review. Biotechnology and Applied Biochemistry. 2020;68(2):404-410. doi:10.1002/bab.1938
2. Sommer C, Kress M. Recent findings on how proinflammatory cytokines cause pain: peripheral mechanisms in inflammatory and neuropathic hyperalgesia. Neuroscience Letters. 2004;361(1-3):184-187. doi:10.1016/j.neulet.2003.12.007
3. Rehling T, Bjørkman AD, Andersen MB, Ekholm O, Molsted S. Diabetes is associated with musculoskeletal pain, osteoarthritis, osteoporosis, and rheumatoid arthritis. Journal of Diabetes Research. 2019;2019:6324348. doi:10.1155/2019/6324348
4. Skovgaard D, Siersma VD, Klausen SB, et al. Chronic hyperglycemia, hypercholesterolemia, and metabolic syndrome are associated with risk of tendon injury. Scandinavian Journal of Medicine & Science in Sports. 2021;31(9):1822-1831. doi:10.1111/sms.13984
5. Roh YH, Lee BK, Kim JK, Noh JH, Gong HS, Baek GH. Effect of metabolic syndrome on the outcome of corticosteroid injection for trigger finger: Matched case-control study. The Journal of Hand Surgery. 2016;41(10):e331-e335. doi:10.1016/j.jhsa.2016.07.091
6. Liu B, Hu Y, Rai SK, Wang M, Hu FB, Sun Q. Low-carbohydrate diet macronutrient quality and weight change. JAMA Network Open. 2023;6(12):e2349552. doi:10.1001/jamanetworkopen.2023.49552
7. American Heart Association. How much sugar is too much? heart.org. Accessed 2024.
8. Weill Cornell Medicine. How excess blood sugar disrupts the immune system. eipm.weill.cornell.edu. Published March 2021.
Medical Disclaimer: This content is for educational purposes only and does not substitute for the medical advice of a physician. Always consult your healthcare provider before beginning any new treatment program. The information presented reflects the opinion of Dr. Jeffrey Peng and does not represent the views of his employers or affiliated hospital systems.
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