For decades, official guidelines urged us to slash fat—especially saturated fat—and fill our plates with grains, fruits, and vegetables to guard our hearts. Yet a thoughtful 2021 review suggests this advice may have backfired for women who already had heart disease.
Quick note upfront: This is not fresh trial data. It is a 2021 Viewpoint in the open-access journal Open Heart by Dr. Timothy Noakes. He re-analyzed long-published results from the huge Women’s Health Initiative Randomized Controlled Dietary Modification Trial (WHI DM Trial).
Launched in 1993, the WHI tested the low-fat pattern pushed by the 1977 U.S. Dietary Guidelines. Almost 49,000 postmenopausal women were randomly split into two groups:
- An intensive low-fat group (targeting 20% calories from fat, plus extra vegetables, fruits, and grains), or
- A control group getting only basic diet tips.
The main 2006 findings (in JAMA) grabbed headlines as “no benefit”: slight weight loss at best, no drop in heart disease, breast cancer, colorectal cancer, or diabetes risk.
But Dr. Noakes spotlights a key detail the original papers downplayed: women who entered the trial with existing coronary heart disease (CHD).
A troubling signal in a vulnerable group
In the 2006 report, these women on the low-fat diet faced a 26% higher risk of another heart event than those sticking to their usual higher-fat eating. By the 13-year follow-up in 2017, that risk rose to 47–61% higher.
This stood out as the only statistically significant result in the 2006 paper. Yet the authors brushed it off, suggesting poor adherence, differences in statin use, or plain chance.
Noakes counters with the trial’s own numbers:
- Statin use stayed similar in both groups for this subgroup (over 40%).
- The trial used “intention-to-treat” analysis, so adherence issues do not erase the findings.
- Original abstracts and conclusions barely mentioned the harm. Later papers even left out this high-risk group to highlight modest gains in healthier women.
Why the downplay?
Noakes argues the results clashed with decades of low-fat dogma baked into national guidelines. The idea that a “heart-healthy” low-fat plan could worsen outcomes in insulin-resistant women (common among postmenopausal women with heart disease) felt unthinkable at the time.
Rather than dig into biology—low-fat, high-carb diets can worsen insulin resistance, a stronger heart risk driver than LDL cholesterol—the authors leaned on post-hoc excuses to keep the “no harm” story intact.
Later analyses, including a 2019 re-look, quietly skipped the CHD subgroup. They focused on healthier women to suggest small benefits. Noakes sees a pattern: shielding the dominant low-fat view instead of facing inconvenient subgroup truths head-on.
What this means for us now
Stronger heart risk predictors in the data were type 2 diabetes (over 10-fold risk) and metabolic syndrome (6-fold risk), not LDL cholesterol.
Noakes stresses that pushing a low-fat diet on postmenopausal women with existing CHD—or clear insulin resistance—may break the “first, do no harm” rule. Newer studies on higher-fat, lower-carb approaches (including ketogenic styles) show promise for tackling insulin resistance.
Bottom line
The WHI remains one of the biggest, costliest diet trials ever. Its “neutral” headline shaped advice for generations. But a close 2021 look reveals a serious warning that got minimized early on.
If you or a loved one has heart disease or signs of insulin resistance, this decades-old data—freshly reviewed in 2021—hints the classic low-fat path may not be harmless. It could even cause harm. Talk with your doctor about options tailored to you. Your heart deserves the best, evidence-based choices.
Sources
- Noakes TD. Hiding unhealthy heart outcomes in a low-fat diet trial: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial finds that postmenopausal women with established coronary heart disease were at increased risk of an adverse outcome if they consumed a low-fat ‘heart-healthy’ diet. Open Heart. 2021;8(2):e001680. https://openheart.bmj.com/content/8/2/e001680
- Howard BV, et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295(6):655-666.
- Prentice RL, et al. Low-fat dietary pattern and cardiovascular disease: results from the Women’s Health Initiative randomized controlled trial and observational study. Am J Clin Nutr. 2017;106(1):35-43.
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