Low carb, low fat, ketogenic…what do these terms mean? What the hell works? Turns out most of them will work if you stick to it *gasp*. There is a lot of frustration when it comes to selecting a diet to lose weight. Oftentimes, on the internet, you’ll find some guru jackass touting the superiority of a low-carb diet or ketogenic or some other type of diet. They also will typically say that this is the only way that works to lose weight and be healthy. A recent position statement by the International Society of Sports Nutrition (ISSN) begs to differ.
The ISSN is a non-profit academic organization dedicated to providing credible and evidence-based nutrition information. They’re the cream of the crop for who you can trust for accurate information. Last month, they released a comprehensive statement-that I’m still reading through-all about diets and body composition. In their statement, they present the research and their interpretation of it on an array of topics relating to diets, dieting, and body composition.
By the way, body composition refers to the literal structure or makeup of your body in terms of how much muscle, fat, water, and other “ingredients” are in your body. A bodybuilder will have a higher percentage of muscle compared to fat and vice versa for a more sedentary person, typically.
“But I don’t have time to read the statement, what does it say?
Well, things that are often great don’t come easy, so you’ll have to put in time to be great at something. But enough life lessons. I know not everyone-unfortunately-isn’t as enthusiastic about reading this stuff as I am, so here are some of the findings summed up from the position statement. In part one of this series, we are going to simply define the different diets and get familiar with them. I will also provide a quick opinion of my thoughts on why these diets work for weight loss. In part two, we will discuss the actual data and the nitty gritty of it all.
Before I begin, I want to say that all of these approaches, when performed properly, can and will lead to weight loss. It’s up to you to decide which approach you want based on your ability to stick with it and whether or not you enjoy it. Dieting shouldn’t be a hellish process, so pick what’s best for you. There’s no one single diet that works for everyone. Okay, without further adieu, Let’s go:
Low Energy Diets and Very Low Energy Diets (LED & VLED)
These two diet types are simple. Consume a small amount of calories to lose weight. LED ranges from 800-1200 calories while VLED is usually defined as 400-800 calories. To be frank, you don’t need research studies to say that these diet types will (typically) cause weight loss. Most people don’t consume such low levels of calories and will most likely begin to lose if they adopt this approach. If someone goes on a VLED diet, the majority of the calories will have to come from protein. You can read more about why that’s the case here.
Low Fat Diets and Very Low Fat Diets (LFD & VLFD)
Keep this in mind as we move forward, the rest of the low- diets do not mean low calorie. You can be low-fat or low-carb or low-whatever, and still consume a lot of calories. They’re not the same thing.
Great. I’m glad you understand. LFD & VLFD usually mean 20-35% and 10-20%, respectively, of your total calories. Often, a low-fat diet can also be thought of as a high-carb diet because that’s usually the case. If the fat is low, the carbs will often be high to make up for the lack of energy-providing sources from fat.
My reasoning for why LFD/VLFD work is because dietary fat is very easy to consume in excess. Let’s take oils. One tiny tablespoon quickly adds up to 126 calories (14g fat x 9 calories/g of fat=126). Let’s be honest, most of us-except me-aren’t measuring their oil usage. So, you likely get a lot more calories from oil than you think you are.
When you decide to go low fat, you’ll likely reduce your total caloric intake since fat is very calorie-dense. This is what will drive the weight loss, fewer calories consumed daily². Fat isn’t evil. You’re not losing weight because you’re consuming less fat, you’re losing weight because less calories are being eaten.
Get it? Got it? Good.
Low Carb Diets & Very Low Carb Diets (LCD & VLCD)
Unfortunately, there isn’t an agreed-upon definition for what a low carb diet consists of. Some think it means less than 45% of your calories comes from carbs while others think low carb is less than 50g per day. I think a safe bet would be anywhere below 45% total calories then adjust it from there based on what you prefer.
Low-carb diets, in my opinion, are the most popular form of dieting as of right now. It’s easy to do because you can usually just eat less of what you’re eating now and not have to make too dramatic of lifestyle changes.
I think the reason it works is once again, less calories being consumed overall in the diet. There isn’t any magical process that happens in your body when you consume less carbs.
I think people believe that because they may adopt healthier habits such as having fruit as a snack instead of cookies or eating more vegetables because they are actively trying to lose weight whereas before, they may not have cared as much. It’s not magic, just more whole foods that contain vitamins, minerals, and fiber. The good stuff!
Ketogenic Diets (KD)
Technically, this is a form of low carb dieting; however, an interesting process occurs in your body to properly call it a ketogenic diet. KD is defined as having a max of 50g carbs in your diet daily or 10% of your total calories. 1.2-1.5 g/kg bodyweight from protein and the remainder is fat, which is roughly 60-80% of your total calories3,4. If you’re an athlete or lifter, your protein should be a bit higher than that to preserve lean mass.
In order to properly do a ketogenic diet, a process known as ketosis needs to occur. Ketosis occurs from excess fat breakdown due to glucose (carbohydrate) not being available to use. An acid known as a ketone begins to get synthesized to replace the glucose that isn’t being made quickly enough from fat; however, this is a process that can take a varying amount of time for the body and brain to adjust to. People will often complain of sluggishness or brain fog when starting a KD. Over time, your body will adjust to being in constant ketosis and you can function normally.
Side note: your body creates ketones daily, but not an amount high enough to trigger ketosis when your carbs are a primary contributor to your diet. The low intake of carbs is the only way to trigger ketosis.
Once again, ketogenic diets are not magic. They’re successful mostly because carbs are the biggest contributor to calorie consumption. When you reduce your intake drastically, coupled with a possible increase in protein (protein is very satiating), you get a net decrease in calories taken in from your diet. Hence, weight loss! Yay!
High Protein Diets (HPD)
HPD are generally defined as being at 25% of total calories or exceeding that level of intake.
There isn’t much to be said about it right now until part two, but my opinion on why they work is because protein is the most satiating macronutrient of the three. This means that protein is filling and helps with feeling full. Due to this, people don’t want to eat as much and consume less calories. Deja vu, right?
Stay tuned for part two! We’re going to look at what the research says about these diet methods and whether some are better than others and suggestions for when to use one over another!
2Hooper LAA, Bunn D, Brown T, Summerbell CD, Skeaff CM. Effects of total fat intake on body weight. Cochrane Database Syst Rev. 2015;7(8):CD011834.
3Westman E, Feinman R, Mavropoulos J, Vernon M, Volek J, Wortman J, et al. Low-carbohydrate nutrition and metabolism. Am J Clin Nutr. 2007;86(2):276–84.
4Paoli A. Ketogenic diet for obesity: friend or foe? Int J Environ Res Public Health. 2014;11(2):2092–107.