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Fat in your diet – what is the truth?

woman measuring fat around her waist

Fat in your diet – what is the truth?

A study published recently has challenged the conventional and widely accepted messages that fat is terrible for our health and the driving force behind the obesity and Type 2 diabetes crisis. Reporting on data from 135,000 people, it claimed that rather than focusing on low-fat diets to improve overall health, we should instead be eating more fat and making an increased effort to moderate our carbohydrate intake. The study found that high carbohydrate diets increase risk of mortality whereas diets high in fat (even saturated fat!) do not. These results contradict current healthy eating guidelines which state that we should eat all types of fat in small amounts and that a large proportion of our diet should be made up of starchy carbohydrates.
The Prospective Urban Rural Epidemiology (PURE) study recorded food intake of people from 18 different nations, including high, middle and low income countries. The study found a significant increase in the risk of death for individuals who have a high carbohydrate intake, while fat – both total fat and saturated and unsaturated fat – were associated with a decreased risk of death. They also found no association between fat and cardiovascular problems, contradicting yet another widely accepted notion that fat contributes to heart disease. The data from the study supported the idea of a moderate daily carbohydrate intake of 55%.

So, what is the truth? When there are so many mixed messages, how can we know that we are doing the right thing?

Well, the PURE study has the benefit of a huge number of participants – the more people giving the data to the research, the more likely it is that these trends are accurate and not simply due to an anomaly in the participant group. It also has support from a number of other studies that have had similar results.
A study in the Lancet: Diabetes and Endocrinology journal found that high carbohydrate intake had the most negative impact on cardiovascular risk factors and that replacing fat with carbohydrates may increase risk for heart disease.
Another study, conducted by Aude et al. on overweight individuals found that individuals on a low carbohydrate diet had a number of health benefits compared to individuals on a low fat diet. The low carbohydrate group lost 1.8 times more weight, had a healthier waist-to-hip ratio and had greater improvements in a number of risk factors for cardiovascular disease. It is important to note that both diets were calorie restricted.
However, even in diets where only the low fat diets are calorie restricted, low carbohydrate (higher fat) diets still demonstrate greater health benefits. A study by Yancy et al. found that even with calorie restrictions on the low fat diet, the low carbohydrate group lost more weight (9.4kg compared to 4.8kg) and had more improvements in cardiovascular disease risk factors.
High fat, high protein and low carbohydrate diets have also been shown to improve memory and brain function and also increase longevity (Buck Institute for Research on Aging).
It is important to note that most of the studies on this topic are being conducted on people with pre-existing health problems including obesity and Type 2 diabetes.

So, perhaps fat isn’t as bad for our health as previously thought… But what about the different types of fat?

We often hear that saturated fat is the enemy, and a significant contributor to heart disease. Despite the new view that mono- and poly- unsaturated fats are the ‘healthy fats’, saturated fat is still demonised. It is true that mono- and poly- unsaturated fat does have a variety of health benefits such as raising good cholesterol and lowering bad, improving brain function and improving overall heart health. However, there is no significant evidence that saturated fat is associated with an increase in either cardiovascular disease or coronary heart disease (Siri-Tarino et al.). In fact, natural saturated fats can actually promote heart health (Dr Axe).

Why might lowering your carbohydrate intake help you to lose weight?

Two of the main reasons that low carbohydrate diets are thought to be so effective in weight reduction are linked to the higher protein intake which is typically associated with low carbohydrate diets. Protein releases energy at a slower rate and so staves off hunger for longer. Low carbohydrate/high protein and fat diets also boost your metabolism and lower your appetite which increases calorie expenditure and reduces calorie intake. They help to prevent the biggest side effect of conscious calorie restriction, which is hunger.
Diabetes.co.uk has long-promoted following a low carbohydrate diet in order to control diabetes and launched a Low Carb Program in 2015. The program welcomed its 250,000th member last month.
Although evidence is beginning to emerge that shows fat may not be as bad for our health (or our waistlines!) as once thought, it is important to recognise that fat has more than double the calories per gram than carbohydrates and protein (9 vs 4 respectively). So, in terms of weight management, it is still important to be mindful when consuming fat to not exceed the daily calorie intake for your body and lifestyle.

All references are available through the following links:

PURE Study: http://www.cardiobrief.org/2017/08/29/huge-diet-study-questions-conventional-wisdom-about-carbs-and-fats/
Lancet: Diabetes and Endocrinology, Aude et al. and Yancy et al.: http://www.healthline.com/nutrition/23-studies-on-low-carb-and-low-fat-diets#section10
Siri-Tarino et al.: http://ajcn.nutrition.org/content/early/2010/01/13/ajcn.2009.27725.abstract
Diabetes.co.uk: http://www.diabetes.co.uk/news/2017/sep/ketogenic-diet-shown-to-improve-memory-and-lifespan-90169425.html Dr Axe: https://draxe.com/healthy-fats/


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