Food impacts on health.
Various popular diets have ranged from low fat to low carbohydrates (carbs) in the past decades with much debate about the better approach to overall health and weight loss.
Dietary guidelines have changed with more data on what should be eaten to attain optimal health and weight.
Recent evidence indicates that while calories matter, food quality plays an equally important role in the maintenance of optimal weight.
Low-fat diets
Low-fat diets were based on the concept that eating less fat, which has more calories than carbohydrates and protein per gramme, would lower caloric intake and prevent obesity.
Furthermore, studies that date back to five decades ago, suggested that low-fat diets might prevent heart disease as high-fat diets were related to high blood cholesterol levels.
By the 1990s, fat-free foods were a regular part of the diets of many countries, with various food pyramids advising sparing consumption of all fats.
In recent years, nutrition guidelines have recognised the nuanced role of fats, i.e. the different types of fats, and promoted moderate intake from healthy sources.
Low-carbohydrate diets
Low-carb diets were initially promoted by American cardiologist Dr Robert Atkins as a weight-loss strategy.
The concept was that the low carb intake would cause the body to use fat for energy requirements.
Various studies reported that the Atkins diet could reduce weight and improve cardiovascular risk factors.
The popularity of this diet peaked in the early 2000s.
Many members of the public have an obsession with low-carb diets, and more recently, high-protein diets, which appear to be a ploy to rebrand highly-processed foods as healthy.
It’s the food, not the diet
Research has shown that the quality of the diet is important for cardiovascular (heart) health.
However, it is less clear whether this is more important than the ratio of carbohydrates, fat and protein a person eats.
There were mixed findings from previous studies of low-fat and low-carb diets for reduction of the risks of coronary artery disease.
Furthermore, there have been few studies of the impact of these dietary patterns in the long term.
The findings of the study titled Effect of Low-Carbohydrate and Low-Fat Diets on Metabolomic Indices and Coronary Heart Disease in US Individuals were published in the Journal of the American College of Cardiology on Feb 11 (2026).
The objective of the study was to prospectively examine the associations of low-fat and low-carb diets, “which emphasise different quantities and qualities of macronutrients, as well as their objective metabolomic indices, with coronary heart disease risk in US individuals”.
The researchers from the Harvard T.H. Chan School of Public Health examined data from 198,473 individuals in three cohort studies with more than 30 years of follow-up.
These were the Nurses’ Health Study (1986-2018, with 64,164 women), the Nurses’ Health Study II (1991-2019, with 91,589 women) and the Health Professionals Follow-Up Study (1986-2016, with 42,720 men).
The participants received food frequency questionnaires by mail every two to four years that inquired about diet, lifestyle factors, medication use and chronic disease diagnoses.
The questionnaires focused on different sources and qualities of macronutrients, i.e. animal products vs plant-based foods, whole grains vs refined carbohydrates, etc.
Based on the responses, the foods were categorised into “healthy” and “unhealthy” low-carb and low-fat diets.
Unhealthy diets were defined as those that favoured animal proteins and fats, potatoes, refined grains, and added sugars.
Healthy diets were defined as those that favoured vegetable proteins and fats, non-starchy vegetables, whole fruits, legumes, and whole grains.
The researchers analysed how low-carb diets, low-fat diets and food quality were associated with coronary heart disease.
These included self-reported coronary revascularisation, non-fatal myocardial infarction (heart attack) and deaths due to coronary heart disease.
Health records were used to confirm heart attacks, and family notifications, postal authorities and national death records to confirm deaths.
In summary, the key findings of the study were that:
- Healthy versions of both low-carb and low-fat diets, which emphasised plant-based foods, whole grains and unsaturated fats, were associated with a significantly lower risk of coronary heart disease.
- Unhealthy versions of both diets, i.e. high in refined carbohydrates and animal-based fats and proteins, were linked to higher risk of coronary heart disease.
- Healthy diet patterns were linked to lower triglycerides, higher high-density lipoprotein cholesterol and lower levels of inflammation.
Metabolomic analyses supported these findings, showing favourable biomarker profiles associated with healthy dietary patterns.
The authors concluded: “These findings highlight the critical role of diet quality in determining health effects of low-carbohydrate and low-fat diets on coronary heart disease risk.
“The healthy versions of these diets may exert their health benefits through some common pathways that, together, entail favourable cardiovascular risk profile and lower coronary heart disease risk.”
Like all studies, there were limitations in this one.
The study population comprised healthcare professionals, so its results might not be widely generalisable.
The dietary intake was self-reported and could be subject to measurement error.
The study also did not assess more extreme dietary patterns, like the ketogenic diet in which carbohydrates typically make up about 5% of total energy intake.
Study senior author Associate Professor Dr Sun Qi stated that the healthy foods the study focused on “are the same foods emphasised by many other healthy dietary patterns: the Mediterranean diet, the DASH diet, the healthy plant-based eating index”, among others.
Moving beyond diets
Journal of the American College of Cardiology editor-in-chief Dr Harian M Krumholz stated: “This study helps move the conversation beyond the long-standing debate over low-carbohydrate versus low-fat diets.
“The findings show that what matters most for heart health is the quality of the foods people eat.
“Whether a diet is lower in carbohydrates or fat, emphasising plant-based foods, whole grains and healthy fats is associated with better cardiovascular outcomes.”
In short, it is the quality of macronutrients, not quantity, that makes a difference for heart health.
A healthy diet is defined by the food choices made.
Low-carb and low-fat diets are associated with lower heart disease risk provided they are rich in high-quality, plant-based foods, and low in animal products.
Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. For more information, email starhealth@thestar.com.my. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
