When it comes to diets, picking between high fat and low fat is difficult. Discover the pros and cons of each diet and how to choose.
In recent decades, the West has undergone a shift in eating patterns from low-fat, high-carbohydrate to a diet which is completely the opposite - a factor which not only impacts your overall health, but also your gut microbiome.
It wasn’t long ago, just several decades, that the medical profession promoted the consumption of low-fat diets to treat heart disease, but recent research has turned this belief on its head. By cutting out the fat in processed foods, more sugar was added to enhance the flavour. Today, low-fat diets are only recommended on a medical basis, they’re not for all.
Table of contents
- High-fat diet vs low-fat diet: what’s the difference?
- Low-carb, high-fat vs healthy diet
- How is a high-fat diet bad for the body?
- Gut health: high or low-fat diet?
- Is a low-fat diet bad for the body?
- High-fat diet and low-fat diet: summary
Your gut is home to trillions of microorganisms including bacteria, which make up a unique ecosystem called your gut microbiome. For your gut microbes to thrive, they need complex carbs for fuel. For that reason, they don’t flourish on high-fat, low-carb diets. They equally won’t flourish on a low-fat, low-carb, high-protein diet!
There’s a distinct difference between dietary and body fat. Dietary fats are the ones you eat, and there are several types, some are good for you, and others bad.
In this case, you are not what you eat. The fat you eat doesn’t automatically deposit itself on your waist, hips, thighs, or bingo wings. The simple act of consuming fat also doesn’t directly raise blood lipids and cholesterol levels.
Contrary to widespread belief, fat is not “bad” in reasonable quantities when you choose the right ones. Low-fat diets may have specific benefits for people with metabolic problems, like high cholesterol and triglycerides, heart problems, and damaged arteries, but if you’re relatively healthy and consume a balanced diet, there’s no need to fear fat.
Unsaturated, saturated, and trans fats
Dietary fats make up one of the three macronutrients (the others are carbohydrates and proteins). Fats are found in both plants and animals. Humans need fats for warmth, energy storage, nerve cell function, and making important things like hormones and vitamins.
The reason plants contain fats is because it provides energy for future baby plants. Their seeds are cushioned in a type of fat which promotes growth. Generally, plant fats are unsaturated and generally considered beneficial and heart healthy. Fish is also a source of unsaturated fats.
On the other hand, beef and pork (especially fatty cuts) are sources of saturated fats – so is dark chicken and whole dairy. Saturated fats stay solid at room temperature (butter or the fat on steak) and should be consumed in moderation.
Trans fats are the one fat that you should strive to avoid, because they’re linked to many diseases including colon cancer, heart disease, and type II diabetes. These partially hydrogenated oils are industrially modified to stay solid at room temperature (like margarine, so it imitates butter). Deep-frying at high temperatures can also cause trans fats to occur.
☝️FACT☝️Processed foods contain less trans fats than before, but they can still be found in cheap processed foods like baked goods, margarine and shortening.
Types of dietary fat
|monounsaturated fats||olive oil, avocado, most nuts|
|polyunsaturated fats||fish, walnuts, seeds, flax, vegetable oils|
|saturated||red meat, lard, whole fat dairy, ghee, butter, cream, coconut oil|
|trans fats||fast food, processed food, dairy, cakes, pastries|
What is a low-fat diet?
A low-fat diet restricts the amount of dietary fat you can eat. Generally, it’s limited to less than 30% of your daily energy intake. However, it can also be determined by the amount of fat consumed in a day, for example, less than 20g.
Often, low-fat diets encourage restricting saturated and trans fats, the ones which are related to adverse health outcomes. They’re often used to promote weight loss or for medical reasons, like metabolic control or protection from heart disease and diabetes.
However, cutting out certain food groups isn’t always healthy. For example, there are certain fats which your body needs to function properly, like omega-3s found in fish, which promote both heart and brain health.
☝️FACT☝️Low-fat processed foods often contain higher levels of sugar which offsets the benefits of cutting fat from the diet, because refined sugar isn’t healthy either .
What is a high-fat diet?
A high-fat diet is essentially the opposite to low-fat. In recent decades, there has been an emergence of diets like low-carb, high-fat like the ketogenic or Atkins diets. Despite their popularity in the mainstream population, there is little data regarding their long-term effects on the body.
When it comes to weight loss, these high fat diets can show promising initial results, however their long-term effects may be less beneficial – and it’s one of the least popular diets. One recent study of 487,759 people showed that people who followed a long-term low-carb diet increased their risk of dying earlier from deadly health problems like cancer, heart disease, and stroke.
FACT Low-carb, high-fat diets are linked with negative changes in the composition of your bacterial ecosystem that can impact your overall health.==
What you eat can greatly impact your overall health. Certain populations across the globe are healthier and live longer compared to some who eat too much of the wrong foods.
The health span of different populations can vary greatly, as can the prevalence of certain chronic conditions, and research pinpoints the role of traditional diet in these effects. Studies highlight important links between food cultures and health outcomes depending on the primary diet followed the people of different locations.
The Mediterranean diet, which is a balanced diet with lots of fiber from plants, olive oil, and moderate meat and fish intake, is associated with greater heart health, healthy body weight, and obesity prevention. The Japanese diet, which contains lots of fish and seafood, with very little refined sugar and animal protein, also helps explain how they stay slim and live longer.
Conversely, the Western diet is linked with a high presence of obesity, type II diabetes, and heart disease. It is made up of large amounts of animal protein, fried foods, and refined sugar, yet is low in complex carbohydrates like vegetables, whole grains, and pulses. It also disrupts gut health by reducing levels of beneficial bacteria which contribute to whole body health.
A higher fat diet replaces carbs with fat as the body’s primary energy source, but too much fat and not enough plants can have consequences for your health.
For many years, we were told that fat is bad, and that is that. Until recently, we struggled to rid ourselves of this idea, but now popular culture has embraced high-fat diets as a quick and easy way to shed extra pounds. Yet somehow, there’s still people buying low-fat milk.
What’s true is that foods like olive oil, avocado, and nuts contain beneficial fats, and the omega-3s present in fish are good for your heart and brain. However, partially hydrogenated trans fats are bad for you – there’s no debating this – and eating too much saturated fat may contribute to obesity.
Metabolism and body weight
Diets like keto are effective for weight loss, but cutting carbs out removes sources of essential things the body and gut bacteria need, like fiber, nutrients, and polyphenols. Equally, choosing the wrong fats in the pursuit of a high-fat diet could have less attractive results.
For example, an increase in saturated fat-rich foods like beef, sausages, cheese, and cream may affect blood cholesterol levels and increase the risk of heart disease. Here, it’s worth remembering that the fiber found in complex carbs actually captures cholesterol and removes it from your system.
You’re probably aware that your diet has a key role in your risk of developing heart disease. It is the leading cause of death worldwide. It affects your heart and your blood vessels because fatty deposits build up in the arteries. As a result, blood can’t flow freely and the blood vessels are less elastic. These deposits can break off and cause a complete or partial blockage, leading to a heart attack.
Saturated fats and trans fats are associated with an increased risk of developing heart disease. Unfortunately, the Western lifestyle is largely to blame because it contains high levels of fats and sugar, which can also damage blood vessels when blood glucose levels are too high for long periods. People who follow the Western diet also have lower rates of physical activity that the body needs to stay healthy.
FACT In the UK alone, one person dies every three minutes from heart and circulatory disease. On average, every day 2,980 people are admitted to hospital for these diseases.==
Heart disease risk factors
- high saturated and trans-fat intake
- physical inactivity
- high levels of low-density lipoprotein (LDL) in the blood
- low levels of high-density lipoprotein (HDL) in the blood
- being overweight or obese
Until recently, the medical world promoted low-fat diets to treat heart disease, but recent research questions this. Instead, there are lots of studies which show that replacing saturated fat intake with polyunsaturated fats, like those in plant oils, can lower your risk of heart disease. So rather than banning all fats, think about what specific fats you should put in your body.
Unbelievably, dietary fat can have a real impact on your brain health. For example, the Western world has seen an increase in brain diseases, including mood disorders. Why? Well, it seems your diet could be a factor.
Recent research has emerged which shows that eating a high-fat diet increases the risk of dementia. Plus, in the short-term, it has side effects like brain fog and reducing your ability to concentrate. It can even make you feel depressed.
A study carried out by Yale University found that eating a high-fat diet can affect the part of the brain which regulates your metabolism and body weight, called the hypothalamus. A high-fat diet causes inflammation in this region causing physiological changes seen in obese people, as well as encouraging increased calorie intake.
Your gut is home to trillions of microbes that work hard each day to keep you in tip-top condition, but when it comes to food, they can be a little fussy too.
Current research suggests that a balanced diet consisting of naturally low-fat plant-based foods like whole grains, legumes, vegetables, seeds, fruit, and nuts is the most beneficial for the gut. Yes, you’re right, that is pretty much the opposite of a high-fat diet.
In fact, a high-fat diet fails to nourish the beneficial bacteria in your gut, leading to lower diversity. Crucially, “good” bacteria perform essential roles that help prevent inflammation, promote gut lining health, and regulate metabolic activities (like blood sugar, weight gain, and blood lipids). So when you have less of them, your whole body feels the effects.
That’s because plant-based foods contain essential energy for your good gut bacteria, known as prebiotics. Prebiotics are different substances, especially different types of dietary fibers (but also resistant starches and polyphenols) that bacteria use to support their existence and perform their health-promoting functions. So a high-fat diet can actually starve them.
Research looking at three diets differing in their fat and carbohydrate content found that individuals fed a diet made up of 20% fat and 60% carbs showed an increase in bacteria that produce butyrate. This short-chain fatty acid prevents inflammation and is the main source of energy for your gut lining.
According to the same study, those on a high-fat diet had increased markers for inflammation in their blood, a risk factor for chronic conditions like cancer and heart disease. However, that’s not to say that all low-fat diets are good. For example, following a Western diet but consuming low-fat dairy isn’t good for your gut microbiome either!
☝FACT☝See how healthy your microbiome is with the Atlas Microbiome Test and get food recommendations for your diet.
Low-fat products often contain more sugar to make them more flavoursome, which means they may not be as good for you as you first thought.
There are many reasons why people choose to follow a low-fat diet, like reducing calories intake, lowering cholesterol levels, or for weight loss. They were once promoted for lowering the risk of heart disease, but subsequent research has found that saturated fat may not be the villain it was once thought to be.
Eating less fat is not necessarily the best way to lose weight or to lower the risk of chronic disease. It’s better to focus on the quality of your diet, increasing your fibre intake, and lowering your intake of processed and fatty meats rather than placing attention on a zero-fat diet.
There is a distinct difference between low-fat and diet high in fat and their effects on the body, including your gut. Aiming to eat a moderate fat diet is healthier because a balanced diet is rich in important macro and micronutrients that your body needs.
Research shows that following a more traditional diet of low-fat and high-carbohydrates keeps your gut microbiome diverse which supports better health. The more diverse your gut is, the better protection you’ll have from chronic diseases.
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- Freeman, L, R et al. Damaging Effects of a High-Fat Diet to the Brain and Cognition: A Review of Proposed Mechanisms, 2014
- Hannon, B, A et al. Obesity: A Systematic Review and Meta-Analysis of Randomized Control Trials, 2017
- Kim, J, D et al. Microglial UCP2 Mediates Inflammation and Obesity Induced by High-Fat Feeding, 2019
- National Health Service. Cardiovascular Disease (CVD), 2019
- Netto Candido, T, L et al. Dysbiosis and Metabolic Endotoxemia Induced by High-Fat Diet, 2018
- Sacks, F, M et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory From The American Heart Association, 2017
- Shively, C, A et al. Mediterranean versus Western Diet Effects on Caloric Intake, Obesity, Metabolism, and Hepatosteatosis in Nonhuman Primates, 2019
- Telle-Hansen, V, H et al. Impact of a Healthy Dietary Pattern on Gut Microbiota and Systemic Inflammation in Humans, 2018
- Wan, Y et al. Effects of Macronutrient Distribution on Weight and Related Cardiometabolic Profile in Healthy Non-Obese Chinese: A 6-Month Randomized Controlled-Feeding Trial, 2017
- Yancy Jr, W, S et al. A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet to Treat Obesity and Hyperlipidemia: A Randomized, Controlled Trial, 2004
- British Heart Foundation, Heart and circulatory diseases in numbers