Can you do both a Low Carb and a Low Fat Diet?

Max Carmody, MSc

You can do both a low carb and low fat diet in theory, but there are many potential issues, that include severe deprivation and lack of dietary variety, losing lean muscle mass, dehydration, and even weakening bones, these diets are not usually recommended.

Low Fat Diets

Low fat diets involve reducing fat intake. Fats are also called fatty acids or lipids, and are made up of a three molecule structure called triglycerides. Fat is one of the bodies major fuel sources. Most of the fat we need is made up by our bodies, but there are some fats that the body cannot make called “essential fats”. There are three main types of fats, unsaturated fats, saturated fats, and trans fats, with unsaturated fat being considered the most healthy, often found in plant products, and trans fat considered the least, found in processed food.

There is no single specific way to follow a low fat diet. Many popular diet plans are low fat but have different approaches to reduce fat intake. Some use things like fat free frozen meals. Some advocate for using less things like butter or cooking oils. Low fat diets have the potential to be healthy, but some eliminate or reduce foods that may provide important nutrients.

Low fat diets typically involve eating lots of fruits and vegetables. They are often big on low fat dairy, such as low fat yogurt, and skim milk. They tend to include a fair amount of carbs, especially healthy carbs like whole grains. This does not automatically mean that they HAVE to be high in carbs, but they tend to be moderate to high carb. They tend to have lots of lean proteins, like skinless chicken breasts, and egg whites. They also sometimes include low fat sweets (although these low fat sweets can be high in sugar). If you would like to read more about what is better, high carb or low carb diets, you can find an article here that I wrote on the topic.

In general, low fat diets limit fat intake to 30% or less of daily consumption, although some can limit it as low as 15%. Many low fat diets exclude eating things like avocados and olives, large amounts of seeds and nuts, non lean meats, high fat sweets and oils like butter or olive oil or canola oil.

Low Carb Diet

Low carb diets limit carbohydrates. Carbohydrates are a type of macronutrient (fat is also a macronutrient) found in many types of foods or beverages. Carbs are made up of fiber, starches, and sugar. Your body then turns them into glucose to function. There are different types of carbs, there are both simple carbs, and complex carbs. Simple carbs are digested quickly, and provide immediate bursts of glucose into the blood stream, and complex carbs are digested more slowly and supply a more steady release of glucose, complex carbs are generally considered to be healthier than simple carbs, although this is not always the case.

Low carb diets can have different ratios of macronutrients (protein, fat, and carbs are the three macronutrients) but they tend to be high in protein or fat, one or the other or sometimes both. As with low fat diets, there are different types of low carb diets. One very popular one right now, the keto diet, is very high fat, moderate protein, and extremely low in carbs. All low carb diets are not as high in fats as the keto diet, some low carb diets prescribe a more moderate amount of fats.

A low carb diet typically focuses heavily on proteins, and non starchy vegetables. They usually limit grains, legumes, fruits, sweets (anything with sugar), pastas, and starchy vegetables, sometimes nuts and seeds. Some low carb diets do still allow small amounts of things like fruits, and whole grains. If you would like to find out about the healthiest ways to do low carb, I wrote an article about it that you can find here.

Similarities and Differences Between Low Carb and Low Fat

As mentioned earlier, there are many different types of both low carb and low fat diets, they are not all the same, so I will only be talking here about what seems to be pretty “standardized”.

Low fat and low carb diets both tend to be big on vegetables. However, low fat diets do not tend to restrict vegetables, pretty much any vegetable is fair game. Low carb diets on the other hand, often restrict “starchy” vegetables. These tend to be vegetables that grow under the ground, like beets and carrots and potatoes. Low fat diets are generally keen on any sort of fruit, whereas low carb diets often restrict any type of fruit except things like berries. It depends on how strictly low carb a person is being, because most fruits do not have that many carbs (although some like bananas, do have a fair amount) but they have some.

A low carb diet tends to be stricter on sweets than a low fat diet. Sugars are carbs, simple carbs, and so a low carb diet will leave out pretty much anything sweet, unless it is sweetened with artificial sweetener. Low fat diets however, can include low fat sweets, that still contain sugar.

Perhaps the biggest difference between low carb and low fat diets, is that typically low fat diets make up for the lack of fat with carbs, especially healthy whole grains, and typically low carb diets tend to make up for the lack of carbs with fats, or sometimes proteins. But low carb diets do usually tend to have at least a moderate level of fat. So is it possible to combine the two?

Can you do both a Low Carb and a Low Fat Diet?

I personally would not do a low fat, low carb diet. I prefer low carb diets to low fat ones, and there’s a lot of research out there showing that low carb diets are more effective than low fat diets. It just seems like too much deprivation to me. Kind of like trying to be gluten free, and a vegan, at the same time.

A low fat, low carb diet may work for weight loss in the short term. It may be possible to pull off, if you work closely with a dietician. But it is a deprivation diet. It can have both short and long term negative health impacts. According to some, it may destroy some of your lean muscle mass. So you will want to be careful about going TOO low on both at the same time. Almost every low carb diet over the past 50 years has been high fat or at least moderate fat, and there is probably good reason for that.

There are some issues with a low carb, low fat diet. One of the main issues, is that if you cut out all the fat and carbs, you are left with just protein, the only other one of the 3 macronutrients. Consuming too much protein can lead to dehydration, and potentially even weaken your bones. You will basically only be eating lean meat, fish, egg white, and a handful of vegetables, and that is going to make it difficult for people to stick with the diet in the long term.

There is a diet called the DASH diet for people with hypertension, however, that although not extremely low carb or low fat, is moderate carb and moderate fat. It emphasizes vegetables, fruits, modest portions of whole grains and healthy fats, lean protein and low fat dairy.

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