For many people around the world—especially those now in their 60s and beyond—the message used to be simple: watch your fat intake. Butter was replaced, eggs were questioned, and supermarket shelves filled with “low-fat” foods that promised better heart health.
It seemed like the right thing to do.
But over time, that clear message has become less certain.
Today, many are asking: Was fat ever the real problem—or have we been overlooking sugar?
The Story Behind the Advice
In the 1960s, early studies suggested that fat and cholesterol were major causes of heart disease. These ideas shaped health advice across many countries for decades.
Years later, a review published in JAMA Internal Medicine found that some of that early research was influenced by funding from the Sugar Research Foundation—and that these ties were not clearly shared at the time.
This does not mean the science was entirely wrong. Many later studies confirmed that certain fats—especially trans fats—can increase the risk of heart disease.
But it does remind us of something important: Science changes over time, and sometimes the full story takes years to uncover.
Fat: Not All the Same
Today, we know that fat is not just one thing.
There are:
- Unhealthy fats (like trans fats in processed foods)
- Saturated fats (found in meat and dairy, best eaten in moderation)
- Healthy fats (found in olive oil, nuts, seeds, and fish)
Research from the Harvard T.H. Chan School of Public Health shows that healthier fats can support heart health, especially when they replace less healthy options.
In short, fat is not the enemy it was once thought to be. The type and amount matter more than cutting it out completely.
Sugar: The Quiet Contributor
While fat was being reduced in many diets, sugar began to play a bigger role.
To make low-fat foods taste better, manufacturers often added sugar. Over time, many everyday foods became sweeter—sometimes without people noticing.
Research has linked high intake of added sugar to:
- Weight gain
- Higher blood pressure
- Increased risk of heart disease
It is also closely linked to Type 2 Diabetes, which can damage the heart over time.
Sugary foods are easy to overeat. They can cause quick rises in blood sugar, followed by drops that leave you feeling hungry again.
When Sugar Can Be Helpful
It may sound surprising, but sugar is not always harmful.
Your body actually relies on sugar (glucose) for energy—especially the brain.
The key difference is where that sugar comes from.
When sugar is found in whole foods like fruit, it comes packaged with fibre, vitamins, and other helpful nutrients.
Research shows that:
- Whole fruits are linked to better long-term health and healthy ageing
- The fibre in fruit helps slow down sugar absorption
- Sugars from whole foods can have neutral—or even beneficial—effects when they replace more processed carbohydrates
Large reviews of nutrition studies have found that fruit intake is associated with:
- Better blood sugar control
- Lower inflammation
- Reduced risk of chronic disease
This is because whole foods contain more than just sugar—they provide a complete nutritional package that supports the body.
That’s why an apple and a sugary snack are not equal, even if both contain sugar.
So, Which One Is Worse?
It is tempting to look for a simple answer: sugar or fat.
But the truth is more balanced.
- Too much unhealthy fat can raise cholesterol and increase heart disease risk
- Too much added sugar can disrupt metabolism and harm the heart
However, sugar in whole foods is generally not the main concern.
The bigger issue is added sugar in processed foods.
A More Sensible Approach
Many experts now suggest stepping away from strict rules about single nutrients.
Instead, the focus is on overall eating patterns:
- Eat more whole foods like vegetables, fruits, and grains
- Include healthy fats in moderate amounts
- Limit processed foods high in added sugar
- Focus on balance rather than restriction
As nutrition researcher David Ludwig has pointed out, focusing only on one nutrient—like fat or sugar—can miss the bigger picture.
The Takeaway
The debate between sugar and fat may never have a simple winner.
But for most people, the advice is clear and practical:
- Be mindful of added sugars, not natural sugars in whole foods
- Choose healthier fats when possible
- Avoid heavily processed foods
- Aim for balance over time
For those who remember the strict low-fat years, this shift may feel surprising.
But it reflects something positive: we now understand that food is more than just fat or sugar—it’s the whole diet that matters.
References
- Kearns CE, Schmidt LA, Glantz SA. Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents. JAMA Internal Medicine (2016)
- Harvard T.H. Chan School of Public Health – Nutrition Source: Fats and Cholesterol
- Dreher ML (2018). Whole fruits and fiber in disease prevention (Nutrients / PubMed indexed)
- Sievenpiper JL et al. Fructose-containing sugars and glycaemic control (BMJ / PMC indexed meta-analysis)
- Gonzalez JT et al. (2024). Impact of sugar source on metabolic health (PMC review)
- David Ludwig – Research on carbohydrates and metabolism
