Here’s a shocking truth: the diet wars might be missing the point entirely. It’s not just about cutting carbs or fats—it’s about what you replace them with. A groundbreaking study published in JACC reveals that both low-carb and low-fat diets can reduce the risk of coronary heart disease (CHD) over 30 years, but only if they’re packed with nutrient-dense, high-quality foods. And this is the part most people miss: diets rich in processed foods, added sugars, and low-quality carbs can actually increase your heart disease risk, regardless of whether they’re low-carb or low-fat.
But here’s where it gets controversial: the study found that diets emphasizing animal protein, animal fat, and processed foods were linked to higher CHD risk, while plant-based, whole-grain, and unsaturated fat-rich versions of these diets were protective. This challenges the idea that all low-carb or low-fat diets are created equal. Lead researcher Zhiyuan Wu, PhD, explains, ‘People can follow the same type of diet using either healthy or unhealthy foods, and that’s where the real difference lies.’
In the U.S., the debate between low-carb and low-fat diets rages on, but this study suggests the focus should shift to diet quality rather than macronutrient composition. Wu adds, ‘Focusing on overall diet quality offers flexibility while supporting heart health.’ But does this align with the latest dietary guidelines? The 2023 U.S. guidelines emphasize ‘real food’ and nutrient-dense choices but also recommend animal protein and full-fat dairy—a point of contention among experts.
Here’s the kicker: While the study supports the guidelines’ focus on whole foods, it contradicts their stance on animal products. Wu notes, ‘Higher intake of saturated fat and animal protein, especially from red meat and full-fat dairy, is linked to higher disease risk.’ This echoes recommendations from the DASH and American Heart Association (AHA) diets, which prioritize plant-based proteins and fats.
Nutrition expert Alice Lichtenstein, DSc, agrees: ‘When comparing animal-based to vegetable-based diets, the latter consistently performs better.’ Yet, she remains hopeful the study will steer attention toward healthy, minimally processed foods—a goal shared by the guidelines. Her advice? ‘Choose whole grains over refined carbs, and opt for fruits and vegetables in their least processed forms.’
The Risks of Unhealthy Diets
The study analyzed data from three large cohorts—over 198,000 participants in total—who completed detailed food-frequency questionnaires over decades. Researchers categorized diets into low-carb and low-fat indices, further dividing them into healthy and unhealthy versions based on food quality. For instance, unhealthy low-carb diets were high in animal fat and protein, while unhealthy low-fat diets were heavy on processed grains and sugars.
The results were eye-opening. Unhealthy low-carb diets increased CHD risk by 14%, while healthy versions reduced it by 15%. Similarly, unhealthy low-fat diets raised risk by 12%, but healthy low-fat diets lowered it by 13%. Wu highlights, ‘The reduction in CHD risk was comparable for high-quality versions of both diets, despite their differing macronutrient focuses.’
Both healthy diets improved metabolomic profiles, suggesting shared mechanisms linking food quality to health. But here’s the burning question: Do these findings support the new dietary guidelines, or do they expose a critical flaw in their recommendations on animal products?
Lichtenstein praises the study’s methodology, emphasizing, ‘It’s the quality of food, not just macronutrient levels, that matters.’ The nutrition field is increasingly moving beyond the low-carb vs. low-fat debate to focus on dietary patterns. As she puts it, ‘Whether it’s Mediterranean, DASH, or vegan, there’s immense overlap in what makes these diets healthy.’
Final Thought: This study isn’t about extreme diets like keto—it’s about moderate, sustainable eating patterns. But it raises a provocative question: Are we overlooking the dangers of animal-heavy diets in favor of convenience or tradition? What’s your take? Do you think the guidelines need a rethink, or is the focus on whole foods enough? Let’s debate in the comments!
