McGill researchers tested 12 diets in mice and found that some high-sugar, high-fat diets were associated with better responses to immunotherapy. The findings may help explain a pattern seen in some cancer studies, but they do not show that gaining weight improves treatment outcomes in people.
Obesity is generally linked to higher cancer incidence and mortality. Yet some studies have found that patients with a higher BMI respond better to immune checkpoint inhibitors. Researchers call this apparent pattern the "obesity paradox." It does not mean obesity is protective overall, and researchers are still trying to explain it.
The study compared 12 diets in mice; it did not test nutrition shakes or protein powders, and it does not establish a serving size, protein target, or Supplement Facts profile for cancer treatment.
What the study may explain, and what it cannot
The researchers suggest that diet-related changes in gut bacteria may affect how the immune system responds to treatment. That makes the microbiome one possible part of the explanation. It does not show that a particular diet will improve immunotherapy response in people. Readers can search PubMed for broader research, but animal studies are not the same as clinical evidence.
The distinction matters for nutrition products, too. A shake marketed for "gut health" may contain fiber such as inulin, chicory root, psyllium, or acacia. But an ingredient's presence does not show that the product changes the microbiome in a meaningful way or affects cancer treatment. Check the Nutrition Facts or Supplement Facts panel for fiber per serving, the full ingredient list, added sugars, serving size, and any proprietary blend that hides individual ingredient amounts.
Claims such as "immune support," "detox," or "clean energy" need the same scrutiny. These phrases do not show that a product prevents or treats disease. The FDA distinguishes structure/function claims from claims to diagnose, treat, cure, or prevent disease in its claims guidance. A wellness claim is not proof of a cancer-related benefit.
What this means for shoppers and patients
The study does not identify a shake, protein powder, sweetener, or single ingredient as the cause of the observed response. It also gives no product formula, clinically effective dose, or serving target for people. Shoppers can compare protein source and grams per serving, total calories, added sugars, fiber type and amount, allergens, and cost per serving. Those details describe a product. They do not show that it affects cancer treatment.
The researchers do not recommend that people with cancer adopt diets designed to cause weight gain. Patients should not change their diet or treatment plan based on this mouse research. They should take nutrition questions to their oncology team or a registered dietitian familiar with their treatment.
The study points to a possible biological pathway for future research. It does not make an "obesogenic" diet a health strategy. The distinction between an association and a proven effect matters beyond oncology. An earlier evidence analysis also noted that an observed association does not prove cause.
For now, the obesity paradox remains a research question about diet, gut bacteria, and immune response. It is not evidence that weight gain, a particular shake, or a "gut health" product improves cancer outcomes.
