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The Controversy with Fats and Weight Gain

Here’s where the controversy about fat and weight loss comes in. In the 1950s, the United States saw a disturbing rise in heart disease and obesity. In fact, in the beginning of the 20th century, heart disease was a rare cause of death, but 50 years later, heart disease became the most common cause of death, which is still the case worldwide. Through autopsy reports, it was found that this was due to coronary atherosclerosis, the narrowing of the blood vessels due to a buildup of plaque, that led to coronary heart disease. 

While countries that had higher rates of heart disease consumed more saturated fat, they also consumed a similar rise in sugar. Image Source

Ancel Keys and John Yudkin’s differing theories on the role of fats in the obesity epidemic

With this epidemic of heart disease facing the United States, scientists including American physiologist Ancel Keys and British physiologist John Yudkin began studying the causes of heart disease and obesity. In particular, these two scientists had differing ideas on the cause of heart disease. Ancel Keys was a popular scientist from the wartime era, and in his famous observational Seven Countries Study, he documented the diet and rates of heart disease in the United States, Finland, Netherlands, Italy, Yugoslavia, Greece, and Japan. 12,763 men were observed and followed up with in 5, 10, and 15 year increments. Through the study, Keys discovered that through differences in diet, the incidence in heart disease is correlated with saturated fat and serum cholesterol, and this was caused by the fat content of their diet. He concluded that dietary fat was to blame for the rise in heart disease. Yet, this study had its controversies – Many noted the fact that France and West Germany were left out of the study because their diets were high in saturated fat but also had low incidence of heart disease, although arguments against this claim state that France was invited to participate in the study, but refused due to a lack of interest. 

Nevertheless, John Yudkin had a differing theory regarding the incidence of heart disease. Yudkin believed that sugar was the cause of heart disease, cavities, liver disease, obesity, and some cancers, which he illustrated in his book, “Pure, White, and Deadly.” Comparing the amount of sugar intake and obesity in the population, there is a clear correlation between the rise in sugar intake as sugar became more accessible, and the rise in obesity. In the graph shown above, countries that increased fat consumption also increased sugar consumption, so sugar could have also been a reasonable explanation for the rise in heart disease. In addition, while humans have consumed saturated fat all throughout history, sugar only became available after the invention of mass agriculture and technology, which Yudkin believed correlated with the rise of obesity in recent years. As we know today, consuming more sugar than the body needs means that the sugar cannot be metabolized by the liver, leading to the excess sugar being stored as fat in a process called de novo lipogenesis. 

But the research we relied on for 40 years may not have been accurate

In this disagreement between Keys and Yudkin, Keys definitively won, and Yudkin was publicly shamed and humiliated, leading to the downfall of his career. In fact, research journals refused to publish his work, he was not allowed to speak at many scientific conferences on nutrition, and other scientists described him as an “eccentric, lone obsessive.” By his death in 1995, Yudkin was long forgotten and had faded into obscurity. By the 1980s, fat was named as the culprit for the rise of heart disease and obesity. During this time, the USDA recommended a diet that was low in saturated fat and cholesterol, and this was the first time that the government advised the public to eat less of a food. Yet, instead of improving health in the country, obesity rates in the United States skyrocketed after the USDA’s recommendation. But why was that? Today, information about nutrition has become more progressive, and many scientists have begun to realize that the dietary information that we relied on for 40 years may not have been accurate. It seemed like unfortunately, Yudkin’s theory was correct. Years after the study, the lead scientist for Italy in Ancel Keys’ famous Seven Countries Study, Alessandro Menotti, found that sugar correlated best with the increase in heart disease, not saturated fat. Many other studies later on also tested low-fat diets on various populations, and found no correlation between saturated fat and heart disease.

“Everything this man [John Yudkin] said in 1972 was the God’s honest truth and if you want to read a true prophecy you find this book… I’m telling you every single thing this guy said has come to pass. I’m in awe… Science took a disastrous detour in ignoring Yudkin. It was to the detriment of the health of millions.”

Robert Lustig, paediatric endocrinologist at the University of California, San Francisco

The sugar industry may have paid researchers to downplay the dangers of sugar

In a paper published in JAMA Internal Medicine, researchers at the University of California, San Francisco found documents that showed that the sugar industry had paid scientists to downplay the dangers of sugar and blame fat instead. For example, in 1965, scientists at Harvard University including Dr. Frederick Stare and Mark Hegsted were paid $6,500, around $49,000 today, by a trade group called the Sugar Research Foundation to write a review paper that would favor sugar, as the studies that showed the correlation between sugar and coronary heart disease were deemed as ‘flawed’ or ‘incompetent,’ concluding that reducing the amount of fat consumed was the best strategy to preventing heart disease. This paper was published in the New England Journal of Medicine. With faulty scientific research, the sugar industry was able to manipulate the public into minimizing the risks of sugar. In fact, according to Stanton Glantz, a co-author on the paper revealing the sugar industry’s involvement with scientists at Harvard, “It was a very smart thing the sugar industry did, because review papers, especially if you get them published in a very prominent journal, tend to shape the overall scientific discussion.”

“We are well aware of your particular interest, and will cover this as well as we can.”

Dr. Mark Hegsted to executives in the sugar industry about their review paper

Even today, the industry still involves itself in shaping scientific studies

Yet, the industry’s involvement in shaping scientific studies is no small issue. Despite the rules by scientific journals today that require scientists to disclose conflicts of interest, scientific studies that favor the industry’s best interests because of funding still go on today. In 2011, a study was published stating that children who ate candy weighed less than those who didn’t, which was a shocking claim. It was discovered that the study was funded by the manufacturers of Butterfingers, Hershey, and Skittles. Additionally, it was also found that Coca-Cola funded multiple studies that deflected the role of sugary drinks in causing the obesity epidemic. In studies that are funded by corporations, it was found that 156 out of the 168 studies had favorable results for the company, and beverage studies funded by companies that manufacture sugary drinks are five times more likely to state that there is no correlation between sugary drinks and obesity. Today, the information available on nutrition, especially regarding the risks of sugars and fats is incredibly divided – some are staunch believers of John Yudkin’s theory and believe that “butter is back,” while others, include the Harvard T. H. Chan School of Public Health, still advocates for the danger of saturated fat. Nevertheless, in any case, balance is the key for a healthy life. While the correlation between saturated fat and sugar with heart disease and obesity may have been questioned over the years, it’s still not healthy to eat high amounts of any food no matter what scientific studies find, so eating in moderation is key to staying healthy.

“Butter may be a ‘middle-of-the-road’ food: a more healthful choice than sugar or starch, such as the white bread or potato on which butter is commonly spread and which have been linked to higher risk of diabetes and cardiovascular disease; and a worse choice than many margarines and cooking oils – those rich in healthy fats such as soybean, canola, flaxseed, and extra virgin olive oils – which would likely lower risk compared with either butter or refined grains, starches, and sugars.”

Laura Pimpin, lead author of “Is Butter Back? A Systematic Review and Meta-Analysis of Butter Consumption and Risk of Cardiovascular Disease, Diabetes, and Total Mortality

Disclaimer: I am not a nutritionist and this is not intended to provide medical advice! Please seek help from a medical professional if you are worried about your weight and intend to lose a drastic amount of weight.

Scientifically, what is the best way to lose weight?

Because of how the body metabolizes food, theoretically, weight gain and weight loss is determined by how many calories the body burns by combining the basal metabolic rate (the minimum number of calories needed to perform basic human functions at rest) and activity level. If energy expenditure and caloric intake are balanced, weight is maintained, but if the body burns more calories than it consumes through food, then it will begin to use its fat storages as energy, which burns fat. A person’s daily caloric needs can be calculated by multiplying their basal metabolic rate with an activity factor (the numbers are listed here!). Since there are 3,500 calories in a pound of fat, reducing the caloric intake by 500 per day means that one pound would be lost in a week.

Exercise also plays a role in fat loss, as it helps burn calories and build muscle. It’s a common misconception that muscle weighs more than fat – Muscle instead has a higher density, so a pound of muscle would take up much less space than a pound of fat. In fact, an argument against the use of the body-mass index (BMI) states that BMI doesn’t accurately portray the body composition because many professional athletes would be considered overweight or obese according to their BMI, but their weight is mostly muscle, not fat. An alternative option to determining body fat are body fat percentages, which measure the percentage of body fat based on a gauge or some calculations. The normal body fat percentage in women is 20-25%, and 8-14% for men, and this is because the female sex hormone, estrogen, stores fat for childbearing in females. Nutritionists often recommend checking weight loss progress based on measurements like how clothes fit rather than the number on the scale, because the scale can’t determine between muscle and fat, so while it may seem like you aren’t losing any weight, it could be because your body is losing fat but gaining muscle. In total, this means that in order to lose weight, the body must consume less calories than it needs to sustain itself daily so it will begin to use its fat storage instead.

Yet, extreme diets can lead to unsustainable weight loss

Given the basics of weight loss, it’s not enough to just eat below your daily caloric needs, your food intake also needs to be healthy in order to be sustainable for weight loss. Yo-yo dieting, which means continuously losing weight and regaining the weight in a cycle, and fad diets that promote extreme weight loss are often not balanced or sustainable in the long term, both of which are necessary to lose weight and keep the weight off. In fact, in a study by Kevin Hall, a researcher in metabolism at the National Institute of Health, and his team, it was found that 80% of the contestants on The Biggest Loser, a reality show for extreme weight loss, regained the weight that they had lost on the show. When faced with extreme dieting, the body attempts to maintain balance by adjusting the metabolism, and this change in metabolism persisted even as the contestants gained more weight, which means that they needed to eat significantly less calories to maintain their weight than typical for a person.

As balance is the key to staying healthy, the best way to lose weight is to eat a healthy and balanced diet that you enjoy, without completely cutting out your favorite foods and instead, eating in moderation through portion control. Given the importance of balance, it’s also important to avoid diets that claim that eating one food only can help you lose weight, such as the mono diet – it’s not possible to survive off of one food, because no one food contains all of the nutrients that the body needs to survive (I actually analyzed this in a blog post here, and I got some pretty interesting results for if you were ever forced to eat only one food for the rest of your life!). Low-fat alternatives may not be the best choice either – Since fat contributes to flavor, low-fat foods often substitute this loss in flavor with additional sugars and unhealthy ingredients that make the low-fat alternative even more unhealthy.

“All my friends were drinking beer and not gaining massive amounts of weight… The moment I started drinking beer, there goes another 20 pounds. I said, ‘This is not right. Something is wrong with my body.’”

Danny Cahill, winner of The Biggest Loser Season 8

How does genetics and physiology impact weight gain?

But what about genetics and physiology? After all, it seems like some people can eat anything and never gain weight while others seem to gain weight just with a single treat. Currently, there have been over 400 genes that have been identified to be linked to obesity, and these genes contribute to differences in body composition, satiety, appetite, cravings, and stress eating. For example, one gene that has been commonly found to cause consistent overeating is the MC4R gene, which produces a hormone that regulates energy intake and expenditure. Many hormones play a role in weight gain, such as leptin, which is responsible for regulating appetite and fat storage, insulin, which is responsible for metabolizing food, and ghrelin, which is known as the “hunger hormone” that increases appetite. Research has suggested that genetics contributes anywhere from 25-80% to a person’s predisposition to be overweight. 

Yet, before the invention of modern technology that allowed food to become easily accessible, having efficient fat storage was a benefit to survival. When a bad harvest or a failed hunt occurred, people who were able to conserve energy and store fat were able to survive better than those who didn’t. Today, despite food being widely available in our modern world, around 85% of people have these genes that confer a predisposition to storing fat and struggle to lose weight as the body tends to hold on to energy. But even more surprising, recent research has been beginning to suggest that our environment can make permanent changes in how our genetics acts in a process called epigenetics. In epigenetics, the actual DNA sequence is not changed but the activity of the gene is changed and can be passed down through generations. During the Dutch Hunger Winter in 1945, the famine caused a change in the metabolism in fetuses, which impacted them throughout their lives. In fact, it was found that the children that were born during the time were heavier and had higher rates of obesity, cardiovascular disease, and diabetes, as well as higher levels of LDL cholesterol and triglycerides. The case of the Dutch Hunger Winter was unique – it was caused by the wartime situation as the Allied forces pushed the Nazis out of the Netherlands and the famine only occurred for a few months before the Allies were able to drop food and supplies into the country. This allowed scientists to study the effect of malnutrition on a specific group of individuals that had suffered a famine at the same time, and they were surprised to find that the conditions during pregnancy could affect the people throughout their lives and change their metabolism through epigenetic changes.

From their function as hormones to the controversies in the world of nutrition, fats are an important macromolecule that plays a critical role in storing energy for the body, but also in insulating the body and transmitting signals. Yet, our growing obesity epidemic in the modern world, researchers are showing that genetics plays a major role in fat distribution, particularly environmental conditions that can change the expression of a gene through epigenetics. Despite the contradictory information and fad diets circulating regarding nutrition, having a balanced and healthy diet is the best way to stay healthy rather than drastic weight loss or restrictive fad diets.

Check out Part 1 to learn about the structure and function of fats!

Fun Fact: I think this article is so far the one I’ve learned the most from! I recently reviewed a couple test questions on biochemistry, and I realized that I could actually answer the questions since I had written and learned about the structure of phospholipids in this blog post, and so many questions make sense now because learning about fats and lipids has allowed me to connect the dots between topics. Fats are truly an interesting molecule!


About the Seven Countries Study. Seven Countries Study | The first study to relate diet with cardiovascular disease. (2019, December 10).

Dalen, J. E., Alpert, J. S., Goldberg, R. J., & Weinstein, R. S. (2014). The epidemic of the 20(th) century: coronary heart disease. The American journal of medicine, 127(9), 807–812.

Johns, D. M., & Oppenheimer, G. M. (2018, March 16). The Made-Up Story About How Big Sugar Shifted the Blame to Fat. Slate Magazine.

(Note: This is an article that opposes blaming the sugar industry for the spread of misleading information about fat! It’s always great to read opposing sides to consider both arguments before forming an opinion. Which side do you think makes the stronger case?)

Kolata, G. (2016, May 2). After ‘The Biggest Loser,’ Their Bodies Fought to Regain Weight. The New York Times.

Leslie, I. (2016, April 7). The sugar conspiracy. The Guardian. .

O’Connor, A. (2014, March 17). Study Questions Fat and Heart Disease Link. The New York Times.

O’Connor, A. (2015, August 9). Coca-Cola Funds Scientists Who Shift Blame for Obesity Away From Bad Diets. The New York Times.

O’Connor, A. (2016, September 12). How the Sugar Industry Shifted Blame to Fat. The New York Times.

Pett, K., Kahn, J., Willett, W., & Katz, D. (2017, August 1). Ancel Keys and the Seven Countries Study: An Evidence-based Response to Revisionist Histories.

The President and Fellows of Harvard College. (2016, April 11). Genes Are Not Destiny. Obesity Prevention Source.

The President and Fellows of Harvard College. (2019, June 24). Why people become overweight. Harvard Health.

Why was Dr. John Yudkin ridiculed & marginalized? Alliance for Human Research Protection. (2016, September 30). 

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