The debate surrounding whether high fat diets are healthy or better for you than high carb low-fat diets remains ongoing.
Is a high fat diet good for weight loss? Is a high fat diet healthy, or does it increase the risk of cardiovascular disease and other health problems? Is a high fat diet better than a high carb diet for weight loss and health?
In this article, we will focus on the pros and cons of a high fat diet, examine the potential risks of a high fat diet, and try to tease out facts from myths about the dangers and benefits of high fat diets.
We will cover the following:
- What Is a High Fat Diet?
- Are High Fat Diets Bad for You?
Let’s jump in!
What Is a High Fat Diet?
Although it sounds somewhat straightforward, there’s actually a fair amount of confusion about what actually constitutes a high fat diet.
There is no single definition of a high fat diet for weight loss, either in terms of the percentage of calories that must be coming from fat or the total number of grams of dietary fat consumed per day in order to qualify as a “high-fat diet.”
Generally speaking, any diet that increases the percentage of calories coming from fat above the standard 30 to 35% may be considered a “high fat diet.”
Thus, when 40% of the total calories come from fat, the person is following a high-fat diet; the same can be said when 75% of the calories come from fat, as is the case with the keto diet.
Moreover, many people conflate a high fat diet for weight loss with a low carb diet, but the two are not necessarily inherently intertwined.
For example, you can eat 50% of your calories from fat, 40% of your calories from carbohydrates, and 10% of your calories from protein.
This would still be a high-fat diet, but it is not a low-carb diet. Note this is a very low protein intake, but those with chronic kidney issues are often advised to follow low-protein diets.
Finally, it’s worth mentioning that although the high fat diet may seem like a relatively new diet fad, this dietary pattern has actually been around for at least one hundred years.
Are High Fat Diets Bad for You?
It’s not uncommon to hear people argue the weight loss benefits of low-carbohydrate diets, but high fat diets have long been criticized for the potential cardiovascular ramifications of consuming certain types of fat in excess.
Although the research demonstrating the dangers of a high fat diet is quite inconclusive at best, suggesting that much of what we thought in the 80s and 90s about the association between fat and cholesterol with heart disease risk may not be all that sound, many people still shy away from consuming a lot of fat.
So, where does the truth lie? Are high fat diets dangerous or bad for you, or are there benefits of a high fat diet?
Let’s look at some of the common claims about the benefits and risks of a high fat diet and try to suss out the facts from the myths.
#1: High Fat Diets Help You Burn More Calories
One of the claims that proponents of high-fat diets make is that consuming a diet high in fat increases your caloric expenditure and helps you burn more calories. This, in turn, helps you lose more weight.
Several studies have overturned this assertion, with results indicating that when people consume the same number of calories per day following a high-fat, low-carb diet or a high-carb, low-fat diet, caloric expenditure is equivalent.
In other words, as long as you are eating the same number of calories on a high-fat, low-carb diet, just because you are eating more fat does not mean that you will burn more calories per day than if you were eating the same number of calories split in a different macronutrient ratio with a high-carbohydrate intake.
Moreover, when people are allowed to eat as many calories as they want, the same results remain; people do not burn more calories per day eating a high-fat, low-carbohydrate diet vs a high-carb, low-fat diet.
In fact, in this particular study, those who were following the high fat diet and had the flexibility to eat as many calories as they wanted actually consumed more calories per day than those on the high-carbohydrate diet with the same caloric intake latitude.
This could potentially increase weight gain on a high fat diet if you are not consciously trying to limit or restrict your caloric intake to meet your total daily energy expenditure (TDEE) or caloric needs based on your body composition and goals (weight loss, weight gain, or weight maintenance).
Verdict: This is a myth; you will not burn more calories on a high-fat diet.
#2: Carbs Increase Fat Gain
One of the more interesting and important discussions entering the debate of high fat vs high carb diets is whether eating excess carbs or excess fat increases the propensity to store extra calories as body fat.
In recent years, with the explosion of popularity in high-fat diets, proponents of high-fat, low-carb diets suggest that one of the high fat diet benefits is that carbohydrates tend to be stored as body fat more efficiently than dietary fat.
Ultimately, it is important to note that any overconsumption of calories beyond your total daily energy expenditure can result in an increase in body fat or adipose tissue.
However, studies have actually shown that dietary fat is stored as body fat more efficiently than carbohydrates.
Fat has been shown to be stored as adipose or body fat at about 96% efficiency, whereas carbohydrates are stored as body fat tissue at only 80% efficiency.
To put this into practical terms, generally speaking, for every 3500 calories you eat in excess of what your body burns, you will store one pound of body fat.
However, this is a rough approximation across all macronutrients, body types, and individual biochemistries and metabolisms.
What the results from this research suggest is that there is actually a fairly large difference in the efficiency of how these excess calories are stored.
For example, because dietary fat has a 96% efficiency to be stored body fat, it seems that you would need to consume about 3,645 calories to gain one pound of fat.
In contrast, with only an 80% efficiency rate to convert excess calories into body fat with carbohydrates, you could consume 4,375 calories of carbohydrates to gain one pound of body fat.
Note that carbohydrates are preferentially converted to glycogen at an efficiency rate of 95%, which is why the propensity to store excess carbs as body fat is lower.
Once glycogen stores are saturated, excess carbohydrates will be stored more readily as body fat.
Verdict: Myth; carbohydrates are not converted to body fat more easily than dietary fat.
#3: Fat Makes You Feel More Full
When you are trying to lose weight in particular, one of the challenges is feeling satiated and keeping your appetite at bay while trying to maintain a caloric deficit.
In other words, if you are consuming fewer calories per day than you are burning in order to try to lose weight, you will likely feel hungry unless you are making deliberate choices with the foods that you are consuming to help keep you fuller for longer on fewer calories.
Proponents of a high-fat diet suggest that one of the benefits of high-fat diets is that it is more satiating and effective at keeping you fuller than other nutrients.
Unfortunately, research hasn’t really backed up this notion.
When studies have compared the satiety factor of different macronutrients, protein always seems to reign supreme.
There are even studies to suggest that carbohydrates are more filling than fats when compared calorie for calorie. This may be due to the fact that carbohydrates contain only 4 calories per gram, which is less than half the caloric density of fat (9 calories per gram).
Thus, you can eat more than twice as many grams of carbohydrates for every gram of fat while still consuming the same number of calories.
Results revealed that high-fat foods such as cheese and peanuts were only about half as satiated as high-carb foods like potatoes and oatmeal.
Researchers also found that foods that weighed the most (highest water content) provided the greatest amount of satiety, with boiled potatoes actually trumping all of the other foods tested in the study.
Fiber and protein content were also positively associated with the satiety factor of the food, whereas fat content was negatively associated with how full people felt after eating.
Furthermore, the result revealed that the satiety ratings indeed correlated with subsequent energy intake.
The fuller that people felt after consuming either a high-carb, high-protein, or high-fat food, the fewer calories they ate in the two hours afterward.
One important caveat here is that the quality of the carbohydrates matters. Carbohydrates with higher water and fiber content were positively associated with feelings of fullness, whereas empty carbs, such as croissants, were much lower on the satiety scale.
One final bit of interesting information that came from this study was the fact that when fat is added, such as a pat of butter, essentially no additional satiety is provided by the food, even though the number of calories will increase significantly.
Overall, according to the National Academy of Sports Medicine (NASM), on average, you get the same amount of satiety from 300 calories of protein as you do from 400 calories of carbohydrates or 800 calories of fat, demonstrating a marked difference in how filling fats are compared to carbohydrates and proteins.
Verdict: Myth; fat is not more satiating than carbs or protein.
#4: You Eat Fewer Calories On a High Fat Diet
Studies have been mixed about the total caloric intake of different macronutrient ratios and diets.
For example, at first, when many people transition to the keto diet, which is one of the most popular high-fat diets, they do consume fewer calories per day overall simply because there are fewer food choices and the abundance of ready-to-eat convenience foods that are high fat or keto diet-approved is extremely limited.
However, while some people do end up lowering their total daily caloric intake on a high-fat diet, research has actually found the opposite to be true long term.
For example, one study found that as the percentage of total daily calories coming from dietary fat increases, total caloric intake per day also increases.
In this study, individuals who consumed about 50% of their calories from fat consumed nearly 750 calories per day compared to individuals who were on a low-fat diet, with only 15 to 20% of their daily calories coming from dietary fat.
In fact, in this particular dietary intervention, the low-fat diet group, which involved consuming 15 to 20% of the daily calories from fat, actually consumed 11.3% fewer calories per day than the medium-fat group (30-35% of the daily calories from dietary fat).
The medium-fat group was essentially the control group from which the other two conditions—high fat diet or low fat diet—were compared.
In contrast to the low fat diet, which resulted in a net caloric deficit relative to the medium-fat diet, the high-fat diet actually resulted in a net surplus of calories (15.4%), meaning those on the high-fat diet actually consumed more calories per day than the medium-fat group, and significantly more calories than the low-fat diet group.
As mentioned previously, another study found that when subjects were allowed to consume as many calories as they would like while following either a high-carb or high-fat diet, those following the high-fat diet ingested significantly more calories per day than those on the high-carb, low-fat diet.
Verdict: Myth; High-fat diets do not cause you to eat fewer calories per day.
#5: High Fat Diets Make You Burn More Fat
Another claim about high-fat diets is that consuming more fat forces your body to burn more fat.
This is actually true.
Studies have found that if you are on a high-fat, low-carb diet, the body preferentially burns fat and becomes more efficient at oxidizing fat for fuel.
However, this does not necessarily translate into better weight loss or body fat reduction.
As is the case with any diet, when you consume more calories than you are burning, you will store excess body fat.
The net balance of your caloric intake versus expenditure matters even though you will be oxidizing more fat when you eat more fat.
Furthermore, one study found that while fat oxidation does increase when you eat more fat, your body may develop a propensity to store more fat, offsetting the slightly fewer calories burned from fat on a low-fat diet.
Verdict: True; you will burn more fat on a high-fat diet, but you may also store fat from excess calories more easily.
Overall, high-fat diets can be helpful for some people, but many of the claims are not well backed by research.
For more information about a specific high-fat diet, check out our guide to whether calories matter on the keto diet here.