Low-fat diets were once believed to be the solution for weight loss and heart health. But science has progressed and nowadays the status quo is up for debate. The question we ask: is a low-fat diet healthy?May 29, 2022 6:12 pm May 12, 2022 5:01 pm
Back to when it all started…
Interest in the low-fat diet began in the 19th century. In fact, low-fat diets were originally praised for their benefits in heart disease prevention and weight loss. In addition, in the 1940s, studies appeared showing a relationship between high fat intakes and high cholesterol levels.
These findings suggested that low fat diets could prevent heart disease in those at risk. After the war and later in the 1960s, low-fat diets became popular with the population in general, not just high-risk heart patients.
From the 1980s onwards, low-fat diets dominated the western diet industry and were promoted by physicians, the government and the media. In the United States, a majority of the population followed the low fat ideology, despite the lack of evidence supporting its role in preventing heart disease or assisting with weight loss.
Interestingly, throughout the same time period during which low-fat diets were gaining traction, the obesity epidemic was born. Nonetheless, the general public and authority figures continued to prescribe to the low-fat diet.(1)
A shift in ideology
In recent years however, there has been a change in the public opinion. Firstly, there has been a surge of low-carbohydrate and keto diets and secondly, more focus has been placed on the differences between types of fats and the awareness that not all fats are equal.
In fact, whilst reputable health authorities, governments and doctors used to recommend reducing fat intake in the diet for heart health, these days the focus has shifted. Instead, the focus is on an overarching healthy and sustainable eating pattern. In other words, people should be emphasizing vegetables, fruit, wholegrains and legumes, with smaller amounts of meat, dairy and sweet foods.
Moreover, focusing on eating more wholefoods and plant-based foods whilst cutting back on processed foods may automatically lower our fat intake, particularly the saturated kind. In fact, saturated fats are typically found in meat and dairy products and can increase our bad cholesterol levels, ultimately leading to heart disease.
However, it’s important to highlight that reducing total fat intake is not a guarantee of improved heart health. Indeed, from the 1980s onwards, the food industry and the population in general began removing fat from their goods and diets respectively. The question is, what did they replace the fat with? The answer: refined carbohydrates and sugars.
“Throughout the same time period during which low-fat diets were gaining traction, the obesity epidemic was born”.
Beware of the “low-fat” trap
Thus, people began eating more bread, biscuits, cookies and low-fat sweetened dairy products such as sweetened yoghurt. Consuming a lot of highly processed carbohydrates spikes our blood sugar levels, leading to insulin release which triggers the uptake of sugar by our body’s cells. This can lead to a blood sugar crash which can make us hungry shortly after. Consequently this can lead to overeating and ultimately weight gain.
Moreover, in general products marketed as low-fat contain high amounts of sugars and other additives to make up for the low fat content.
In addition, regular consumption of highly processed carbohydrates and simple sugars can lead to insulin resistance. In other words, this means that in the long term, overconsumption of these foods can impair our body’s natural ability to respond to insulin, in the worst case scenarios this can lead to diabetes.
Moreover, diabetes and overweight/obesity are tightly linked to an increased risk of developing heart disease. Ironically, by avoiding fat in order to reduce the risk of heart disease, compensating with unhealthy carbohydrates seems to lead to the same outcome which we had originally tried to avoid.
What’s more, by avoiding all fats we are also avoiding healthy unsaturated fats. In fact, fats found in olive oil, nuts, seeds, avocados and fish are healthy fats that actually promote cardiovascular health.
Low-fat vs Mediterranean: which is better for heart health?
What is the evidence regarding the impact of a low-fat diet on cardiovascular risk factors? And how does it compare to the trusted mediterranean diet?
A group of researchers conducted a meta-analysis looking at randomized controlled trials comparing low-fat diets to the Mediterranean diet. Moreover, the studies included trials performed in overweight/obese individuals followed-up for at least 6 months. The authors analyzed 6 randomized controlled trials in total including 2650 participants, of which half were women. The average age of participants was between 35 and 68 years.(2)
The results showed that at a 2-year follow-up, individuals in the Mediterranean group had more favorable outcomes compared to individuals in the low-fat diet group. In fact, participants assigned to the Mediterranean diet had a lower body weight, lower blood pressure, lower blood glucose levels and lower total cholesterol levels compared to their low-fat diet counterparts.
Overall, it appears that the Mediterranean diet is more favorable than a low-fat diet when it comes to modifying cardiovascular risk factors. What’s more, these results are clinically significant in the long-term.
Low-fat vs Mediterranean for Type 2 diabetes
It’s no secret that keeping your blood sugars in check is a high priority if you have diabetes. We know from the literature that what you eat has a powerful and direct impact on blood sugar levels. But how does a low-fat diet affect our blood sugar? A team of researchers looked into the effects of a low-fat diet compared to mediterranean diets on several parameters related to glycemic control in individuals with type 2 diabetes.
Three dietary interventions were carried out on a total of 191 individuals. 2 groups followed a Mediterranean diet supplemented with either olive oil or nuts, whereas a third group followed a low-fat diet. The researchers measured changes in body weight, waist circumference and insulin resistance. The results showed that the mediterranean diets led to a significant reduction in body weight, however the low-fat diet did not. Insulin resistance significantly improved across all diets.(3)
Overall, it seems that the mediterranean diet supplemented with either olive oil or mixed nuts is just as effective as a low-fat diet in improving glucose metabolism.
Not all fats are created equal
It’s important to distinguish between saturated fats and unsaturated fats. Whilst the former are known to increase LDL cholesterol, the latter offer beneficial effects for heart health.
It’s a well known fact that saturated fats are linked to increased cholesterol levels and poor heart health. These types of fats are predominantly found in animal products (such as butter) but also in some plant sources such as coconut and palm oil. In order to ensure healthy cholesterol levels, we should aim to replace saturated fats with unsaturated fats. In particular, substituting saturated fats with monounsaturated fats and polyunsaturated fats can help to decrease “bad” LDL cholesterol.
Healthy unsaturated fats
The healthiest sources of monounsaturated fats include extra virgin olive oil and almond oil. In fact, extra virgin olive oil consumption is directly related to a reduction in “bad” LDL cholesterol, and reduced risk of cardiovascular disease and mortality.(4)
Moreover, pumpkin seed oil and black seed oil are excellent sources of healthy polyunsaturated heart healthy fats.
In addition, nuts are an excellent source of healthy fats which can reduce cholesterol. Nuts also contain fiber which can mitigate some of the bad cholesterol from being absorbed into the bloodstream from the gut. Various clinical studies have consistently shown that nuts lower total and LDL cholesterol. Moreover, it is thought that the favorable fatty acid profile of nuts (i.e. low saturated fats and high unsaturated fats) lowers cholesterol thus also reducing the risk of coronary heart disease.
A summary of the literature found that nuts can reduce LDL cholesterol by up to 19% compared to Western and lower-fat diets. What’s more, the plant sterols and antioxidants naturally found in nuts may also favorably impact cholesterol.
Overall, nuts have a unique nutrient profile and can be included as part of a healthy diet alongside many heart-friendly foods. Moreover, it appears that diets including nuts may have stronger cholesterol-lowering effects than general diets used to lower cardiovascular risk which do not include nuts.(5)
One handful per day is a good amount. You can eat them as a snack or add them to salads, yoghurt or porridge. Ideally, choose the raw unsalted varieties for the best nutritional profile.(6)