Obesity is rapidly emerging as one of the most significant and preventable drivers of cancer, and new scientific evidence suggests it is something we have to pay attention to now.

A major review published in the JAMA reports that obesity now contributes to roughly 10 per cent of all new cancer diagnoses in the US each year. While the data are drawn from American populations, the data points that the biological mechanisms involved are universal.

The findings are therefore highly relevant to countries such as Malaysia, where obesity rates have risen sharply over the past two decades.

The review highlights a troubling reality. Excess body weight does not simply coexist with cancer risk. It actively reshapes the body at a cellular level, creating internal conditions that allow cancer to form, grow, and spread.

Scientists have now linked obesity to at least 13 types of cancer, including colorectal, liver, pancreatic, kidney, ovarian, thyroid, and post-menopausal breast cancers. These are cancers already seen with increasing frequency across Southeast Asia, including in Malaysia.

Although the study focuses on the US, we have to emphasise that the underlying biology does not change across borders, ethnicities, or healthcare systems. Fat tissue behaves in the same way in all human bodies. Chronic inflammation, hormonal disruption, and metabolic stress follow similar patterns regardless of geography. This makes the conclusions directly applicable to any country facing a growing obesity burden.

Malaysia is one such country. National health surveys consistently show high and rising obesity rates among adults, with growing concern about childhood obesity as well. Urbanisation, sedentary lifestyles, high intake of ultra-processed foods, and sugary beverages have all contributed to this trend. Health experts warn that without decisive prevention strategies, Malaysia may see a parallel rise in obesity-related cancers in the years ahead.

The review explains why obesity is such a powerful cancer driver. Fat tissue is not biologically inert. It functions as an active organ, releasing hormones, inflammatory chemicals, and growth signals. When excess fat accumulates, it leads to long-term, low-grade inflammation throughout the body. This chronic inflammatory state provides fertile ground for cancer to develop.

Most tumours arise within or near fat tissue. In an inflamed environment, damaged cells are exposed to constant growth signals and an expanded blood supply. If a cancerous mutation occurs, the surrounding tissue can support its progression into a tumour. Researchers describe this as a “host environment” that encourages cancer growth rather than suppressing it.

Cancer cells share several defining features. They can divide without limit, resist programmed cell death, create their own blood vessels, and evade immune surveillance. Many also alter their metabolism to consume excess energy. Obesity accelerates nearly all of these processes. Elevated insulin levels, hormonal imbalance, and increased availability of nutrients give cancer cells the tools they need to thrive.

Genetic damage plays a central role. Obesity increases oxidative stress and inflammatory signalling, both of which can damage DNA. At the same time, the body’s ability to repair this damage appears to weaken. Over time, this combination increases the likelihood that a normal cell will become cancerous.

The immune system is also affected. Excess body fat reduces the effectiveness of immune cells that normally identify and eliminate abnormal cells. Natural killer cells and T cells become less responsive. This allows early cancer cells to escape detection and establish tumours.

Gut health is another important factor. Obesity alters the balance of gut bacteria, reducing populations that produce anti-inflammatory compounds. The gut lining becomes more permeable, allowing inflammatory substances to enter the bloodstream. This process adds to systemic inflammation and may further increase cancer risk. These mechanisms are not specific to Western diets or lifestyles and have been observed in diverse populations worldwide.

Duration of obesity matters. The longer a person lives with a body mass index in the obesity range, the greater the cumulative biological damage. The review found that prolonged exposure makes it harder to reverse harmful changes later in life. This finding has particular relevance for Malaysia, where obesity is increasingly seen at younger ages.

Weight loss can improve many of the biological disturbances linked to obesity, but only if it is meaningful and sustained. The researchers note that losing more than 10 per cent of body weight may help reduce inflammation and metabolic stress associated with cancer. However, short-term weight loss followed by regain may do more harm than good.

Repeated cycles of rapid weight loss and regain place additional stress on fat tissue. Each cycle triggers contraction and expansion, increasing inflammation. This so-called weight cycling may worsen the internal conditions that promote cancer. Long-term weight stability is therefore as important as weight reduction.

Prevention emerges as the most effective strategy. Addressing obesity early in life offers the greatest potential to reduce cancer risk decades later. For Malaysia, this underscores the importance of school-based nutrition programmes, active transport, accessible recreational spaces, and policies that reduce exposure to high-sugar and highly processed foods.

Medical advances also offer new tools. Drugs that mimic the hormone GLP‑1, initially developed to treat type 2 diabetes, have shown strong effects on weight reduction. A large 2024 study involving more than 1.6 million patients in the US found that people using GLP‑1 medications had a significantly lower risk of several obesity-related cancers compared with those using insulin. These included cancers of the liver, pancreas, and colon.

While such medications are becoming more widely available in Malaysia, experts caution that they are not a standalone solution. Weight regain is common when treatment stops without a long-term plan. Sudden rebound weight gain may intensify inflammation and metabolic stress. Sustainable lifestyle changes remain essential to maintain benefits and protect long-term health. Always consult you medical professionals for medical advice.

Dietary habits play a central role. Nutrition experts often recommend simple, culturally adaptable strategies rather than rigid diets. One widely supported approach is the plate method. Half of the plate is filled with vegetables and fruit, emphasising fibre and natural anti-inflammatory compounds. One quarter is lean protein, such as fish, poultry, eggs, or plant-based options. The remaining quarter consists of whole grains.

Reducing intake of processed meats, refined carbohydrates, and sugary drinks can significantly lower inflammation. Replacing sweetened beverages with water or unsweetened tea is a practical and effective step.

Mindful eating is another recommended strategy. It encourages awareness of hunger and fullness cues, slower eating, and reduced distractions during meals. This approach helps break cycles of extreme dieting and overeating. Balance is key, allowing occasional indulgence without guilt while maintaining overall healthy patterns.

Physical activity remains a powerful protective factor. Current guidelines recommend at least 150 minutes of moderate-intensity exercise per week. This can include brisk walking, cycling, swimming, or active household tasks. Strength training at least twice a week is also encouraged to build muscle mass and support metabolism.

Exercise offers benefits that go beyond weight control. Regular physical activity stimulates immune cells that identify and destroy abnormal cells, counteracting the immune suppression associated with obesity. It also improves insulin sensitivity and reduces inflammation, directly addressing pathways linked to cancer development.

The broader message from the review is both cautionary and hopeful. Obesity is now one of the most important modifiable risk factors for cancer. Its effects are profound but not inevitable. While the study data come from the United States, the biological principles apply globally, including in Malaysia.

Cancer prevention is often discussed in terms of screening and treatment. This research reframes the conversation.

Preventing obesity, especially from childhood, may be one of the most effective cancer prevention strategies available. In Malaysia, where non-communicable diseases already place heavy strain on the healthcare system, acting on this evidence could have far-reaching benefits.

Excess weight is not merely a lifestyle issue. It is a complex medical condition with deep biological consequences. Understanding its link to cancer, and responding early and decisively, could help shape a healthier future for Malaysians.