Fat or Fiction: Is Dietary Fat Really That Bad For You?

Are you guilty of gravitating toward the low-fat yoghurt, cereal, or snack options at the grocery store? I sure am. Have you ever stopped to consider why you choose these options over full-fat varieties? It’s likely due to the (apparent) health benefits of a lower-fat diet. But are low-fat foods really that much better for you? Rather than thinking of dietary fat intake as “all-or-nothing”, it’s better to consider that fat comes in many “shapes and sizes”, some are good for our health and some are not. Throughout this article, we’ll take a look at the research that has taken place, predominately in America across the late 20th century, and how this has had a profound influence on the subsequent government dietary recommendations that have been released. This has had flow-on effects and has influenced our preference for low-fat foods in the modern era. Let’s take a look at how we got to where we are today, demonising dietary fat as a whole and unnecessarily contributing to this low-fat diet culture we still experience. 

A Brief History of the Progression of Dietary Fat Guidelines

1950s: The Seven Countries Study

The bad reputation of dietary fat in the modern world originated in one study called The Seven Countries Study. It was a pioneering investigation conducted by Dr. Ancel Keys and his colleagues in the mid-20th century. Dr. Keys was an American physiologist and nutritionist who initiated the study to examine the relationship between diet, lifestyle, and cardiovascular disease (CVD) across different populations around the world. The study began in 1956 and involved approximately 12,763 men aged 40 to 59 from seven countries. These countries were the United States, Finland, the Netherlands, Italy, Greece, Yugoslavia, and Japan. The primary focus of the Seven Countries Study was to investigate the association between dietary factors, particularly fat consumption, and the prevalence of coronary heart disease (CHD). Researchers collected extensive data on participants’ dietary habits, lifestyle factors, medical histories, and physical measurements. Dietary information was gathered through detailed surveys and interviews.

Dr. Ancel Keys and his team analysed the data over several years, examining correlations between dietary fat intake and the incidence of CHD across the seven countries. The study found a correlation between high dietary intake of saturated fats, elevated serum cholesterol levels, and increased rates of CHD in populations such as those in the United States and Finland. While the study provided valuable insights into the relationship between diet, lifestyle, and cardiovascular disease (CVD), it also faced several scientific issues and criticisms over the years:

1. Sampling Bias: The study’s selection of countries was not necessarily representative of global populations. The chosen countries were primarily from Western Europe and Japan, and they may not have accurately represented diverse dietary patterns and lifestyles worldwide. This limited the ability to generalise the study’s findings to other populations.

2. Cross-sectional Design: The study primarily used cross-sectional data, meaning that data was collected at a single point in time. Cross-sectional studies can establish associations but cannot establish causation. Therefore, while the study found associations between dietary fat and CVD risk, it could not definitively prove that dietary fat caused heart disease.

3. Dietary Assessment Methods: The dietary assessment methods used in the study were based on food frequency questionnaires and surveys, which are prone to recall bias and inaccuracies. Participants may have misreported their dietary intake, leading to unreliable data on fat consumption.

4. Limited Dietary Variables: The study focused primarily on total fat and saturated fat consumption and did not adequately consider other dietary factors that could influence CVD risks, such as dietary fibre, specific types of fats (e.g., trans fats), and overall dietary patterns.

5. Selective Data Reporting: Critics have argued that Ancel Keys and his colleagues selectively reported and analysed data to support the cholesterol hypothesis and their recommendations to reduce dietary fat intake. Some researchers have suggested that including all available data would have yielded less conclusive results regarding the association between dietary fat and CVD.

6. Changes in Diet and Lifestyle: The study spanned several decades, during which dietary habits and lifestyle factors changed significantly in many of the participating countries. Changes in diet, smoking rates, physical activity levels, and other factors could have influenced the incidence of CVD independently of dietary fat intake.

The results of the study advocated for low-fat diets as a means of reducing the risk of heart disease. As such, it prompted the development and widespread availability of low-fat and fat-free food products, aligning with the public’s growing interest in health-conscious dietary choices. Additionally, the study’s association between dietary fat, serum cholesterol levels, and heart disease risk led to guidelines advising on the limitation of dietary cholesterol, influencing recommendations to decrease the consumption of cholesterol-rich foods such as eggs and certain meats (which we now know is unnecessary). 

The study had a significant influence on the development of the first national dietary guidelines released by the U.S. Senate Select Committee on Nutrition and Human Needs in 1977. These guidelines, known as the “Dietary Goals for the United States,” were formulated in response to growing concerns about rising rates of heart disease and other diet-related health issues in the United States. 

Let’s take a closer look at these.

1977: Dietary Goals for the United States

In 1977, after years of discussion, scientific review, and debate, the U.S. Senate Select Committee on Nutrition and Human Needs released the first national dietary guidelines for the United States called “Dietary Goals”. In summary, these dietary goals recommended the following:

1. To avoid being overweight, consume only as much energy as is expended; if overweight, decrease energy intake and increase energy expenditure.
2. Increase the consumption of complex carbohydrates and “naturally occurring” sugars from about 28% of intake to about 48% of energy intake.
3. Reduce the consumption of refined and processed sugars by about 45% to account for about 10% of total energy intake.
4. Reduce overall fat consumption from approximately 40% to about 30% of energy intake.
5. Reduce saturated fat consumption to account for about 10% of total energy intake; and balance that with polyunsaturated and monounsaturated fats, which should account for about 10% of energy intake each.
6. Reduce cholesterol consumption to about 300 milligrams a day.
7. Limit the intake of sodium by reducing the intake of salt to about 5 grams a day.

Recommendations ‘d’ and ‘e’ were partly based on the idea that consuming fat promotes obesity because fat is the most concentrated source of energy in the diet.

1980

In February 1980, the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (HHS) collaboratively issued the release of “Nutrition and Your Health: Dietary Guidelines for Americans”. These guidelines were a response to increasing concerns about diet-related health issues, particularly cardiovascular disease.

One of the key recommendations outlined in the Dietary Guidelines for Americans relates to dietary fat intake. The guidelines advised Americans to limit their consumption of total fat, saturated fat, and cholesterol to reduce the risk of heart disease. Specifically, the guidelines recommended that individuals should aim to:

1. Limit Total Fat Intake: The guidelines recommended that individuals should consume a diet low in total fat, emphasising the importance of choosing lean sources of protein and reducing the consumption of high-fat foods such as fatty meats, full-fat dairy products, and fried foods.
2. Reduce Saturated Fat: Recognising the role of saturated fat in raising blood cholesterol levels and increasing the risk of cardiovascular disease, the guidelines advised Americans to reduce their intake of saturated fats. This included limiting the consumption of foods high in saturated fats, such as butter, cheese, red meat, and certain processed foods.
3. Moderate Cholesterol Intake: The guidelines recommended moderating cholesterol intake by limiting the consumption of foods rich in cholesterol, such as egg yolks and organ meats. While the dietary cholesterol recommendation was later removed from subsequent editions of the guidelines due to evolving scientific understanding, the advice to limit high-cholesterol foods remained part of the dietary guidance.

These recommendations on dietary fat reflected the broader scientific consensus at the time, influenced by research including the Seven Countries Study and other epidemiological investigations. The guidelines aimed to provide clear and actionable advice to the American public to promote heart health and reduce the risk of chronic diseases associated with poor dietary habits. 

1984

The initial recommendations to reduce dietary fat were reinforced in 1984 by an expert panel at the NIH Consensus Development Conference on Lowering Blood Cholesterol to Prevent Heart Disease. This was a pivotal event that continued to shape dietary guidelines and public health recommendations regarding fat intake. 

Here’s a summary of the recommendations on dietary fat presented at the conference:

1. Limit Saturated Fat Intake: One of the key recommendations was to limit the consumption of saturated fats. Saturated fats, found primarily in animal products such as meat and dairy, were identified as a major contributor to elevated blood cholesterol levels, which are associated with an increased risk of heart disease.
   
2. Reduce Dietary Cholesterol: Participants at the conference also advised reducing dietary cholesterol intake. Foods high in cholesterol, such as egg yolks and organ meats, were singled out as contributors to elevated blood cholesterol levels and were recommended to be consumed in moderation.
   
3. Increase Polyunsaturated and Monounsaturated Fats: The conference highlighted the importance of replacing saturated fats with healthier alternatives, such as polyunsaturated and monounsaturated fats. Sources of these healthier fats include vegetable oils (e.g., olive oil, canola oil, soybean oil), nuts, seeds, and fish.
   
4. Choose Low-Fat Dairy: Recommendations included opting for low-fat or non-fat dairy products to reduce saturated fat intake while still obtaining essential nutrients like calcium and vitamin D.
   
5. Moderate Total Fat Intake: While the emphasis was on reducing saturated fat intake, the conference also acknowledged the importance of moderating total fat consumption. While fat is a necessary component of the diet, excessive intake can lead to weight gain and other health issues.
   
6. Consider Individual Health Status: The recommendations emphasised that dietary fat guidelines should be tailored to individual health status and risk factors for heart disease. Factors such as age, gender, family history, and existing medical conditions were deemed important considerations in determining appropriate dietary fat intake levels.

A Closer Look At The Low-Fat Trend

Starting in the 1970s, as we’ve explored above, Americans were told that avoiding fat in their diet would help prevent fat accumulation in their bodies. Influential nutrition experts confidently theorised that fats encouraged overeating, while carbohydrates, including sugar, appeared to curb it. The shift towards low-fat diets led to a corresponding increase in carbohydrate consumption, particularly refined carbohydrates and sugars. This dietary change resulted in many individuals replacing fats with processed carbohydrates, such as white bread, pasta, and sugary snacks. Because of this, the U.S. government’s “Healthy People” initiative in the year 2000 urged the food industry to produce and market processed low-fat foods. In addition, the notorious Food Guide Pyramid of 1992 in the U.S. prioritised a broad range of processed carbohydrates (ranging from 6 to 11 daily servings) at the base, relegating all fats to the top.  This kick-started the glorification of the low-fat food trend we still see today and may account for why you instinctively choose these options at the supermarket. 

Throughout this era, fat intake neared the recommended 30% of total calories as per the dietary guidelines at the time, so we should have seen reductions in overweight and obesity and improvements in heart health. However, this was far from the case. We actually witnessed a surge in the obesity epidemic, with an increased incidence of metabolic disease. Interesting, right? 

Keep reading as we explore why this was the case. 

Rethinking Dietary Fat

Contrary to earlier beliefs, it should be obvious now that not all fats are detrimental to our health. Essential fatty acids and certain types of fats play crucial roles in our metabolic health. By focusing solely on reducing total fat intake, guidelines may have inadvertently encouraged the consumption of low-quality fats while neglecting the importance of healthy fats in regulating lipid metabolism and insulin sensitivity. In addition to this, dietary fat plays a role in hormonal regulation, including the secretion of insulin and leptin, which are hormones that affect appetite and energy expenditure. Low-fat diets, particularly those high in refined carbohydrates, can disrupt these hormonal signals, leading to dysregulated appetite control and metabolic dysfunction. Consequently, we may experience increased hunger, cravings for high-calorie foods, and difficulty maintaining a healthy weight.

As we’ve previously mentioned, dietary fats come in many “shapes and sizes”, some good for us, and some not so much. Each type of fat has a unique chemical structure and effect on our health. Let’s explore this further.

Saturated fats are solid at room temperature and are commonly found in animal products such as meat, dairy, and eggs, as well as some plant-based oils like coconut oil and palm oil. These fats have been linked to an increase in LDL cholesterol levels (“bad” cholesterol) in the blood, which is a risk factor for cardiovascular disease when consumed in excess.

Monounsaturated fats, typically liquid at room temperature, are found in foods such as olive oil, avocados, nuts, and seeds. They are considered heart-healthy fats because they can help reduce LDL cholesterol levels while maintaining or increasing levels of HDL cholesterol (“good” cholesterol), which is beneficial for our heart health. Polyunsaturated fats, also liquid at room temperature, include omega-3 and omega-6 fatty acids. Omega-3 fatty acids, found in fatty fish, flaxseeds, and walnuts, have anti-inflammatory properties that benefit heart health. Omega-6 fatty acids, found in vegetable oils, are essential for health but may promote inflammation if not balanced properly with omega-3 fatty acids.

When discussing “bad” fats, we need to shed a (massive!) spotlight on trans fats. They are actually a type of unsaturated fat that can occur naturally in some animal-based foods but are primarily created through an industrial process called hydrogenation (i.e. they are man-made). They are found in processed and fried foods, baked goods, and margarine. These fats raise LDL cholesterol (“bad” cholesterol) levels and lower HDL cholesterol (“good” cholesterol) levels, increasing the risk of cardiovascular disease. Trans fats have been associated with inflammation, insulin resistance, and other negative health effects. Many health authorities recommend minimising or eliminating trans fats from the diet altogether. So this leads us to believe we shouldn’t be “pigeon-holing” dietary fat as ‘good’ or ‘bad’. Instead, we need to consider the nuances that make up a well-balanced and holistic diet. 

A Fresh Look at Fats

A significant complexity in understanding dietary fats lies in the fact that few foods consist solely of one type of fat and various types of fat typically come from multiple food sources. While there’s solid evidence supporting monounsaturated and polyunsaturated fats as beneficial, and saturated and trans fats as detrimental, some of the healthiest oils, such as olive oil, canola oil, and soybean oil, also contain unhealthy saturated fat. Similarly, red and processed meats are rich sources of unhealthy saturated fat, but they also contain monounsaturated fat, which is generally considered a healthy fat. Therefore, it’s preferable to approach fats by considering their whole food sources, opting for foods that predominantly contain “friendly” fats while limiting consumption of those foods that predominantly contain unhealthy fats.

The global dietary landscape has been profoundly shaped by decades of research, recommendations, and societal shifts regarding fat consumption. From the emergence of low-fat diet trends in the 1950s to the establishment of dietary guidelines in subsequent years, our perception of dietary fat has undergone significant evolution. Despite the initial intention to improve public health, the emphasis on reducing fat intake has inadvertently led to the widespread consumption of low-quality fats and highly processed carbohydrates, contributing to the obesity epidemic and metabolic diseases we observe today.

As we reevaluate the role of dietary fats on our health, it becomes evident that not all fats are created equal. While excess saturated and trans fats are associated with adverse health effects, monounsaturated and polyunsaturated fats offer numerous benefits for heart health and overall well-being. By shifting our focus from solely demonising fat to understanding its nuances and incorporating whole food sources rich in beneficial fats, we can make more informed dietary choices that promote long-term health. Moving forward, we should adopt a balanced approach to fat consumption, considering the diverse types of fats found in different foods and their respective health implications. Rather than adhering strictly to low-fat dietary guidelines, we should prioritise whole, nutrient-dense foods and mindful eating habits. By embracing a fresh perspective on fats and their role in our diet, we can generate a sustainable approach to nutrition that supports our optimal health.

REFERENCES

• Yngve A. (2009). A Historical Perspective of the Understanding of the Link between Diet and Coronary Heart Disease. American journal of lifestyle medicine, 3(1 Suppl.), 35S–38S. https://doi.org/10.1177/1559827609334887
• Ebbeling, C. B., Young, I. S., Lichtenstein, A. H., Ludwig, D. S., McKinley, M., Perez-Escamilla, R., & Rimm, E. (2018). Dietary Fat: Friend or Foe?. Clinical chemistry, 64(1), 34–41. https://doi.org/10.1373/clinchem.2017.274084
• Dietary Guidelines for Americans. (n.d). History of the Dietary Guidelines. Dietary Guidelines for Americans. https://www.dietaryguidelines.gov/about-dietary-guidelines/history-dietary-guidelines
• Keys, A., Menotti, A., Aravanis, C., Blackburn, H., Djordjevic, B. S., Buzina, R., Dontas, A. S., Fidanza, F., Karvonen, M. J., & Kimura, N. (1984). The seven countries study: 2,289 deaths in 15 years. Preventive medicine, 13(2), 141–154. https://doi.org/10.1016/0091-7435(84)90047-1

• Bio

Ellyn Johnson

Ellyn is an Exercise Scientist specialising in youth Strength and Conditioning. She holds her Bachelor's degrees in Science and Exercise and Sports Science. She has previously worked as a Strength and Conditioning Coach for Academy level athletes at the Brisbane Lions Football Club. She has a background in Personal Training, coaching a range of clientele with diverse goals, including weight loss, body recomposition as well as recreational endurance athletes. In addition to her Strength and Conditioning experience, Ellyn currently works as a Learning Designer at the Australian Institute of Fitness. Here she works as a subject matter expert in the design and implementation of a range of health- and fitness-related courses and learning materials.