New research findings justifies another look at this topic we have covered before, but this is not easy with very polarised views. It used to be simple in the past. What’s now considered flawed research stated that fat, particularly saturated fat, was bad for our health. It increased cholesterol levels and caused heart disease with early death. Low-fat diets were in vogue and industry produced plenty of low-fat alternatives for the proselytes.
Unfortunately, industry substituted fat with sugar and that didn’t help the situation much. Actually, it now seems to have made what was considered a bad situation even worse.
Fight between old and new science
In a previous blog I put my toe into the sugar debate, an issue that has recently turned nutrition on its head. Now overindulgence in sugar is the culprit behind several diseases and increased mortality. So in the one corner we have the old die-hard supporters of the low-fat diet, while in the other corner we have the fresh newcomers daring to promote a low-carb high-fat diet.
Although the low-fat supporters have lost considerable ground the umpire seems to still be sitting on the fence. The 2015-2020 Dietary Guidelines for Americans target both saturated fats and added sugars as nutrients to limit and seem to give them equal weight in their advice:
- Consume less than 10% of calories per day from added sugars, and also
- Consume less than 10% of calories per day from saturated fats.
Let’s just pause for a moment to consider this new advice. The energy stored in our food is measured in terms of calories. Technically, one calorie is the amount of energy required to raise the temperature of 1 gram of water 1º Celsius. However, in the food area a calorie is actually 1000 technical calories. Although the technical calorie unit is part of the metric system, it has been superseded in the International System of Units by the joule and used in some countries as the new energy measure. A food calorie is approximately 4.2 kilojoules. Confused, I thought so. So for convenience let’s stick to the common use of calorie in the food area and forget that technically it is actually kilocalories.
Now to be clear, sugar contains less than 4 calories, whilst fat contains 9 calories per gram. Thus, according to the above recommendations you could consume double the amount of added sugar compared to saturated fat to keep within the given proportion of energy allocated to each of the two nutrients. So although the recommendation looks evenhanded in reality it is not.
New studies support the low-carb camp
Back to the science. With the tables turning, low-fat diets are out and high-fat diets are very much in. Since the eat-less-saturated-fat advice has been around for decades, there should be proof around either way you would think. However, it took quite some time to disprove the fat hypothesis since it was considered heresy.
This has changed and a new article cites several meta-analyses of randomised controlled trials that did not find a connection between saturated fats and heart disease or overall death rates.
But it goes further with low-carb comparisons. A recent study suggested that low-fat diets might not be the way to go after placing about 150 adults on either a low-carb or a low-fat diet for a year. Participants on the low-carb diet lost more weight and lowered their risk for heart disease more than participants who followed a low-fat diet.
Another study involved 17 people at risk for heart disease and diabetes. They were put on a low-carb, high-fat diet for three weeks. Then, they turned the table and increased carb intake while reducing total fat and saturated fat intake every three weeks for 18 weeks, keeping total caloric intake the same. The more carbs and less fat in the diet resulted in an increase in markers linked to obesity, type 2 diabetes, and heart disease. I know, a very small group of people, but anyway.
So is the fight over?
No, we are still waiting for the knock-out blow. Life is never that simple.
As for saturated fats, these fats are a diverse class of compounds. Some saturated fats elevate bad cholesterol, others have no effect, and some actually increase good cholesterol. Fats in foods are always a mixture. While some foods high in saturated fats, such as processed meats, might be connected to heart disease, other foods high in saturated fat such as dairy have no such effect. And there is also the supposition that some polyunsaturated fats might induce inflammation that in turn can influence the heart disease rate.
And similarly to fats, not all carbs are equal. The monosaccharide, fructose, and the disaccharide sucrose, common table sugar, with half fructose (together with glucose), produce greater degrees of metabolic abnormalities than does glucose alone found in long chains of starch in certain foods and cellulose in plant walls.
If you need to lose weight science is pretty clear. If you eat too little fat, your metabolism won’t be as efficient and will create some waste because of an excess of carbs and/or protein. A slower metabolism and a higher load of waste will interfere with weight loss. On the other hand, high-fat food dampens appetite and can help you eat less and thus lose weight.
Sugar can be fattening indirectly by causing you to eat more. Eating too much sugar will encourage insulin production. If you produce too much insulin it actually causes blood sugar to dip and you feel tired. As you need an energy boost you eat more, and you tend to give in to cravings for more sugar. Of course, that only makes the whole cycle happen again.
But we don’t eat fat or carbohydrates in isolation, we eat them in the form of complex foods with a lot of other necessary components. If you forget weight loss and just want to maintain a healthy diet there is room for good forms of both fat and carbohydrates. With fat you get important fat-soluble vitamins and essential fatty acids, and with complex carbohydrate foods you get minerals, water-soluble vitamins and antioxidants like flavonoids.
What about everything in moderation?
We have said it before, why not everything in moderation as the saying goes. Or did go!
Even that has now been criticised as being too vague and difficult to measure. ‘There are no good or bad foods,” and “all foods can fit into a healthy diet” are variations on the moderation theme. But what exactly is moderation? A new study found that definitions of moderate consumption were related to personal consumption behaviours. Results suggest that the endorsement of moderation messages allows for a wide range of interpretations of moderate consumption.
Healthy eating is about finding a balance between two extremes – deprivation and overindulgence. It is about adhering to strategies and habits that can be maintained long term as part of a lifestyle to avoid a yoyo effect between these extremes.
Call it what you like as long as you don’t give in to your ghrelin urge too often. An occasional binge can be justified to keep you happy. That’s what life is all about, isn’t it?