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New diet study challenges old theories about weight loss, fat and severe calorie restriction

Yet another study the Dietary Science Foundation has supported has been published; this time a study of diet and obesity. The results go against several established theories in the area. Participants lost a substantial amount of weight despite an almost normal calorie intake. The amount of fat or carbohydrate in the diet made no difference as far as weight reduction and the study gives reason to question whether saturated fat really is a significant cause of fatty liver. 

In 2018 the Dietary Science Foundation helped fund a study of diet for obesity. It was designed to examine how the amount and quality of carbohydrates influence weight loss, and how saturated fat affects the body. The first results of the study have now been published in the scientific journal Clinical Nutrition.  Let’s start with some background information.

Two different low-fat diets and one low-carbohydrate diet tested

In the study, which was carried out in Bergen, Norway, the researchers allotted 193 people between 20-55 years of age with abdominal fat to three different diets. The first was a traditional low-fat diet with very little added sugar and relatively large amounts of wholemeal flour. Here are examples of a breakfast and a dinner:

 A traditional low-fat diet with a lot of wholemeal flour and a minimum of added sugar, but juice was included.

The second was a so-called cellular low-fat diet with minimally processed raw ingredients; for example potatoes and fruit were to be eaten whole, not as mashed potatoes or a smoothie. Grains were to be consumed preferentially as whole grains and not as milled flour. It could look like this:

 A cellular low-fat diet with a lot of whole grains. Fruit was eaten whole, not as juice, and there was minimal added sugar.

The third diet included very little carbohydrate. 70 percent of energy came from fat, of which almost half was saturated fat. Here are examples of meals from this diet:

 A strict low-carbohydrate diet. 30 percent of calories were from saturated fat, with a total fat percentage of 70 percent. 

What all the diets had in common was that participants ate a lot of vegetables and natural foods. The amount of added sugar was extremely small. Female participants were encouraged to eat 2,000 calories per day and male participants 2,500. So what happened?

Major weight loss despite normal caloric intake 

The answer is that there was hardly any difference at all between the groups. This might seem like an unexciting result, but it challenges several established theories in the field. The first is that participants on average lost 6–8 kg despite eating basically normal portions.

“What we’re seeing is that it’s not necessary to reduce energy intakt as much as people often do to reduce their weight. In the long term it can be better to eat more normal amounts so people don’t give up,” says Simon Dankel, professor at the University of Bergen, who led the study.

More fat in the diet just as effective as more fiber

The study also challenges the view that you need to reduce fat intake and eat more fiber to lose weight. In the low-carbohydrate group about two-thirds of calories came from fat, nearly twice as much as the low-fat group. And despite eating about half the amount of fiber, participants lost just as much weight as the other groups. A greater reduction in waist circumference could even be seen in the low-carbohydrate group during the first few months of the study. 

“Fiber intake didn’t change at all when participants started eating a low-carbohydrate diet. So the weight loss can’t be explained by more fiber,” says Simon Dankel. 

Saturated fat did not cause fatty liver

Another interesting result from the study is that the amount of liver fat was markedly reduced in all groups, even in the low-carbohydrate group which consumed a lot of butter and cream. Earlier studies from among others Uppsala University in Sweden had indicated that saturated fat is bad for the liver, but this study does not support that hypothesis. Instead, the study confirmed the result from another study financed by the Dietary Science Foundation, where both a strict low-carbohydrate diet and intermittent fasting reduced the amount of fat in the liver more effectively than conventional treatment. 

Why did participants lose weight?

How was it possible for participants to lose so much weight without a drastically restricting calorie intake? 

“One reason might be that as long as you reduce your intake of added sugar and ultra-processed food, and primarily eat food made from high quality ingredients, it doesn’t make much difference what you eat,” says Simon Dankel. 

This kind of conclusion is in line with several other studies that have been published in recent years. One of them is the DIETFITS study out of Stanford University in the USA. In that study participants ate either a low-carbohydrate or a low-fat diet, both of which were based on natural ingredients. Both diets included a lot of vegetables and participants were instructed to minimized the amount of added sugar, wheat flour and other ultra-processed foods. Despite the fact that they didn’t need to count calories, participant lost on average 5–6 kg during the year of the study, and there was no significant difference between the groups. 

One weakness: a high drop-out rate

One weakness in the study from Bergen is that an unusual number of participants dropped out. After six months just 78 people were left and after one year only 57 people. The researchers believe that the high drop-out rate was because the study was very demanding. Participants were given a recipe collection that they were to follow exactly. One of the reasons was so the amount of unsaturated fat could be held constant between the groups. 

“We made very high demands on participants to follow our recipes at every meal and we think it got too stressful for many of them in the long run.”

The drop-out rate was extra high in the group assigned to a traditional low-fat diet with a lot of flour. In that group just 14 people completed the study, compared to 21 and 22 people in the other groups. 

“There are two possible explanations. The first is that the food was perceived to be less healthy since it contained more wheat flour. The other is that it actually worked less well and that people left the study because they didn’t get the desired effect.”

People in the other two groups may also have dropped out because the diet either made them feel bad or they didn’t get the desired effect.

Difficult to track people’s eating habits

Another weakness (and this is true for pretty much all dietary studies) is that it’s difficult to track people’s eating habits. According to the researchers’ measurements participants hardly reduced their calorie intake at all, yet they still lost weight. But the analysis was done according to what participants themselves reported they ate. It’s well known in the field of dietary research that many people underreport what they eat. That’s why it’s hard to know how much calorie intake was actually reduced. But the researchers encouraged both men and women to eat a normal amount of calories, so weight loss was probably not due to a drastic decrease in calories.

Analyses of blood lipids and gut flora soon to be published

When it comes to a strict low-carbohydrate diet with a lot of saturated fat, one worry is that it can cause a dangerous elevation of “bad” LDL cholesterol. The researchers did very exact measurements of how the different blood lipids were affected by the diet. These results will be published at a later date, but Simon Dankel can already reveal that the preliminary analyses do not show any alarming effects of the low-carbohydrate diet. 

Do you want to lose weight? Eat better quality food

So what conclusions can be drawn from the results of this study? There is mounting evidence that conventional healthcare has gotten it wrong when it comes to helping people lose weight. Until recently the focus has been on drastically limiting calorie intake, but it looks like it’s time to shift the focus to the quality of the food. When we eat high quality food it appears that most of us automatically eat a normal amount of energy. 

“At the same time it’s important to point out that the study was done on people under 50. Older people often have a lower metabolic rate and for them other things may be involved. My conclusion is that if you’re very overweight and are between 20-50 years old, it doesn’t make any difference if you eat fiber-rich carbohydrates or fat. The most important thing is that you reduce your intake of refined carbohydrates,” says Kerstin Brismar, professor of diabetes research and chairman of the Dietary Science Foundation’s scientific advisory board. 

Isn’t this good news? There’s so much wonderful, natural food to enjoy. Thank you to everyone who supports us! It helps us finance studies that increase our knowledge of how diet affects us. If you’re not already a monthly donor you can join us here

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