Eating less processed foods gave weight loss and lower risk of heart disease – also among men on a high fat diet
The quality of the food you eat may be as important to your health as whether you eat lots of fat or carbohydrates, according to a new Norwegian study.
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The debate about fat and carbohydrates – and their importance for the risk of obesity and lifestyle diseases – has been around for a long time.
People with belly fat have traditionally been advised to cut fat and calories from their diet. However, several researchers believe that carbohydrates – like sugar, bread and potatoes – are the biggest problem.
In the last few years studies have been suggesting that the proportions of fat and carbohydrates may not play as big a role as we thought. Maybe even calories have been overrated.
Recently, one more study points in this direction.
Fat men on two different diets
Vivian Veum and her colleagues at the University of Bergen are the researchers behind the new research. Veum recruited 40 men with overweight or abdominal obesity and put them on a diet for three months.
Half of the group were instructed to eat relatively little fat and a lot of carbohydrates. The other half were told to eat a lot of fat – including a lot of saturated fat – and very few carbohydrates.
Apart from this difference, the food they ate was similar.
Both groups consumed the same amount of protein and calories. And most importantly, everyone was instructed to eat as little sugar and as few highly processed foods as possible.
Sweets, soda and refined cereal products and oils were out, and less-processed vegetables, nuts, beans, seeds and berries were in. Both groups were to eat half a kilo of vegetables a day.
The food for both groups was based on the same ingredients, only in different ratios, and all the participants ate the same types of fat and complex carbohydrates.
Participants were given a collection of detailed recipes and ingredient lists that they used during the three months of the experiment. The men recorded what they ate and how active they were. The researchers took several measurements both pre-experiment and after four, eight and twelve weeks of being on the diet.
Thinner and healthier
After three months, the results showed clear and positive effects in both groups.
On average, the men in both the low-fat group and the high-fat group had lost more than 10 kilos. Their waist measurements had shrunk by 10 centimetres and they had significantly less dangerous visceral fat around their internal organs. Fatty liver was also reduced equally by both diets.
"Both groups also ended up with better blood sugar levels and a more favourable distribution of fats in the blood," says Veum.
One difference did show up between the groups, however. The men on the low-fat diet immediately had lower LDL cholesterol levels in their blood. LDL cholesterol is linked to increased risk of heart disease and is often referred to as 'the bad cholesterol'.
The men eating a lot of fat experienced a slight increase in LDL cholesterol, especially the first few weeks. By the end of the study, however, the LDL level had dropped slightly again.
This isn’t surprising.
Numerous studies, most of them short-term, have shown that high levels of saturated fat in the diet can increase LDL cholesterol levels. But some longitudinal studies have shown that cholesterol levels drop again over time.
Numerous studies have documented that consuming a lot of saturated fat often raises LDL cholesterol in the short term, but it is still uncertain what happens if you eat a lot of saturated fat and low carbohydrates over a longer period of time.
Different LDL particles
Veum believes that a slightly elevated level of LDL cholesterol does not necessarily imply an increased risk of heart disease.
Not all LDL particles in the blood are the same, she says. They can be small and dense or large and fluffy. Several studies have suggested that small LDL particles are the troublemakers.
If the rise in LDL cholesterol is mainly due to large particles, this may not pose a greater risk of heart disease, according to Veum, who is currently working on a research article on this very topic.
“LDL cholesterol has to be seen in connection with other factors. If the level of triglycerides – another fat in the blood – is low, and the good HDL cholesterol is high, elevated LDL cholesterol is unlikely to pose a problem,” she says.
Both low levels of triglycerides and high HDL cholesterol appear to protect against heart disease.
Quality makes a difference
Clinical nutrition physiologist Tine Mejlbo Sundför, a doctoral fellow at Oslo University Hospital, did not participate in Veum's study. She thinks it is an exciting and well-conducted study.
“The results are based on the fact that the quality of the food makes a difference,” she says.
“This is the new research buzz at the moment: the kind of foods you eat may play as important a role for your health as the distribution of fat and carbohydrates.”
Mejlbo Sundför gives an example. “Unsalted nuts with a high fat and calorie content are being hailed as a "super food" with many essential nutrients and positive health effects, whereas pretzels are low fat snacks with relatively few calories, but they’re made from refined wheat flour and a lot of salt that don’t have positive health effects.”
Still, she warns people not to have the impression that they can just load up on fat.
“It’s well documented that elevated LDL cholesterol increases the risk of cardiovascular disease,” she says.
Some people are also genetically predisposed to getting high cholesterol. They have to be careful.
In a Norwegian study done in 2018 and published in the journal Atherosclerosis, healthy students ate low-carbohydrate and high-fat diets for three weeks. During this time, the average LDL cholesterol increased by 44 per cent, compared to the control group. But the results varied widely among the study participants.
Some had only minor changes in their LDL cholesterol, while others more than doubled their levels.
Different effects on normal weight and obese individuals
Mejlbo Sundför says some research actually suggests that changing one’s saturated fat consumption can have different effects on normal weight and obese individuals.
“A lot of people with obesity do not have high LDL cholesterol but high levels of triglycerides and low HDL cholesterol,” she says.
Mejlbo Sundför and her colleagues recently published a study showing that the effect of high saturated fat was different in normal weight and obese people.
Among the overweight participants, an increased intake of saturated fat did not appear to particularly affect LDL cholesterol. Normal weight participants, on the other hand, experienced the expected increase.
So if you are obese but don’t have very high LDL cholesterol, would it maybe be more important to cut back on sugar and white flour to achieve a greater reduction in triglycerides and a better effect on blood sugar regulation?
Same advice doesn’t fit for everyone
There are a lot of indications that different people experience different effects from the food they eat.
“Veum's study doesn’t disprove dietary advice. But it’s not a given that we should give the same advice to everyone,” says Mejlbo Sundför.
“If you’re obese and find it easier to achieve a healthier diet and weight loss with a low-carb diet and more fat, that may be an option,” Mejlbo Sundför says.
Lifestyle changes are always difficult at first, and you may not be able to manage everything at once.
“It might be more important to concentrate on cutting out sugar and refined carbohydrates,” she says.
But Mejlbo Sundför still wonders if one needs to reduce carbohydrates as much as in Veum's study, where men got only 10 per cent of their energy from carbohydrates, and over 70 per cent from fat?
Diet doesn’t have to be extreme
Veum herself does not think an extreme low-carb diet – a so-called ketogenic diet – is necessarily the key.
“We used a diet with a lot of fat for our research context, to get clear results, but I think the participants could achieve similar results with a greater proportion of the right carbohydrates, she says.
Veum completely agrees with Mejlbo Sundför that the same advice is not suitable for everyone.
“Although saturated fat isn’t that problematic in itself, how much each individual should eat can vary. At the same time, we know that in obese and insulin-resistant people, cholesterol gets worse from carbohydrates, whereas fat intake causes fewer problems,” Mejlbo Sundför says.
“The point is to eat a low-glycaemic diet with fewer processed foods, in order to achieve stable blood sugar levels,” she says.
“Then caloric intake regulates itself more naturally because appetite and satiety hormones work better. We eat more in line with our physiological needs and don’t crave simple carbohydrates because our blood sugar is more stable,” Mejlbo Sundför adds.
“You can actually eat more calories without gaining weight, because you’re in a better mood and your body can expend a little more energy,” she says.
Veum says the men in the study actually lost a lot of weight, without a dramatic cut in calories.
Moderate calorie reduction
The men consumed about 500 fewer calories than they were used to, but still ate about 2 150 calories a day.
By comparison, the crispbread regimen at the Morbid Obesity Center in Vestfold Hospital Trust results in a corresponding weight loss over three months, but with a diet of only 800 to 1200 calories a day.
“The number of calories wasn’t decisive for the result. Several participants didn’t reduce their caloric intake at all, but they still lost fat, both in their subcutaneous fat and visceral fat,” says Veum.
She believes this shows that counting calories doesn’t necessarily give us a good picture of the body’s energy conversion.
The body is no oven
Calories are basically a measure of how much heat is generated when you burn different materials in a furnace. The idea is that a certain amount of energy enters the body, and what is not consumed for bodily functions and activity is stored as fat.
But the energy conversion in the body is not as predictable as the one in the furnace. It adjusts itself by several different regulatory mechanisms, for example through the hormone system and the nervous system.
For example, it is well documented that people who aggressively lose weight lower their metabolism. If you lose a lot of weight, you have to eat less than a similar person who has never lost weight. If not, you’ll gain the weight back again.
Previous experiments have also shown that humans react very differently to eating too many calories. Some people gain a lot of weight, while others hardly notice any change in weight.
The body is apparently capable of adjusting how it uses the incoming energy.
A number of studies also indicate that you actually don’t burn more calories the more you move.
In addition, studies have shown that the bacterial composition in our gut flora make a difference in how many calories the body is able to use from the food we consume.
Long-term effects still unknown
Veum says that participants in both groups in the study were surprised at how much food they were allowed to eat.
“They asked me: ‘Is this really a diet?’” said Veum.
“It was a great study to do. After getting used to things, the participants were very satisfied. They felt satiated, had stable blood sugar and stopped craving unhealthy foods,” she says.
How likely it is that they would have remained satisfied with the diet over time – or perhaps permanently – we don’t know. The study only lasted three months. The men were motivated and avoided some social activities where it could be more difficult to stick to the diet.
It’s a known fact that the pounds you lose on a diet tend to creep back afterwards if you don’t manage to maintain the new lifestyle.
It is also a matter of whether the diets would provide the beneficial effects to the body at a time when participants weren’t losing weight but were in maintenance mode. A lot of research shows that losing weight in itself improves the levels of fats and sugars in the blood, regardless of how healthy the diet is.
“It would be interesting to do a similar study on weight-stable people, and see if the differences in fat intake have an effect on the fat stores in the body,” says Veum.
So there’s still a lot we don’t know.
But Veum's study joins a growing number of studies that point to the importance of food quality.
No matter who you are, replacing highly processed foods with less processed ingredients appears to be beneficial for everyone.
Reference:
V. L. Veum et.al: «Visceral adiposity and metabolic syndrome after very high-fat and low-fat isocaloric diets: a randomized controlled trial», American Journal of Clinical Nutrition, Jan 2017.
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Translated by: Ingrid P. Nuse
Read the Norwegian version of this article at forskning.no
