Low-Fat Vs. Low-Carb Diets — The Risks And Benefits – Fitnessnacks

    As a strength athlete, you’re accustomed to thinking about the weight on the barbell. But if you’re also thinking about the weight on the scale, you’re probably also thinking about what you’re cooking up in the kitchen.

    Nutrition plays a huge role in everything from getting stronger to building muscle. When you’re searching for ways to eat healthier or lose weight, you might come across various types of restrictive diets. Low-fat and low-carb diets both feature heavily in many gyms — and on plenty of social media platforms.

    Plates of low-fat food and low-carb food.Credit: Adam Melnyk / Shutterstock

    With all the talk about losing fat in fitness circles, the nuts and oils of the world get a pretty bad reputation. But do low-fat diets actually help you lose fat? Are carbs actually the enemy? Read on to learn about low-carb versus low-fat diets.

    Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.

    If you or anyone you know are struggling with disordered eating habits, the National Eating Disorders Helpline is available at various hours throughout the week online and by texting or dialing (800) 931-2237.

    What Is a Low-Fat Diet?

    In a low-fat diet, you’ll get less than 30 percent of your daily calories from fat. (1) If 30 percent sounds like a lot, keep in mind that one gram of fat contains significantly more calories than a single gram of carbohydrates or protein.

    To get a perspective of how very little fat you would eat on a low-fat diet, bear with some quick and easy calculations. (We’ll do all the actual math for you.)

    • One gram of fat = nine calories
    • One gram of protein = four calories
    • One gram of carbohydrates = four calories

    In a 2,000-calorie diet, 30 percent of the total caloric intake is 600 calories, and 15 percent is 300 calories.

    This means that it would take just over 67 grams of fat to yield 600 calories, while it would take 150 grams of protein or carbs. For perspective, just one tablespoon of peanut butter typically contains eight grams of fat.

    An open jar and a teaspoon of peanut butter.Credit: Shyripa Alexandr / Shutterstock

    It’s easy to see how few grams of fat are involved in low-fat diets. And remember, the calculations here are for 30 percent of your caloric intake. That’s the high end of a low-fat diet.

    On the lower end of a low-fat diet, only three tablespoons of peanut butter would get someone to their low-fat daily intake — and that’s without any olive oil or any other source of dietary fat in your diet.

    Different Kinds of Low-Fat Diets

    Fat is only one of three macronutrients (the other two being protein and carbohydrates). Not to mention all those micronutrients and vitamins that your body needs to function optimally. A diet can be very low in fat but not very high in protein, or low in fat but high in very processed foods. 

    Just one component — low-fat — is not necessarily enough to paint a picture of the entire diet. In that sense, there are many low-fat and low-carb diets out there, all of which are very different than each other based on what components make up the rest of the diet.

    What Is a Low-Carb Diet?

    There’s no consensus about what constitutes a low-carb diet. However, when researchers study these diets, they often define a diet as low-carb when less than 26 percent of your daily caloric intake will be carbohydrates. (2)

    For reference, the United States Department of Health and Human Services and the Department of Agriculture (USDA)’s Dietary Guidelines for Americans recommend that 45 to 65 percent of daily caloric intake comes from carbohydrates. (3)

    Dipping much below those recommendations may not be safe in the long run. Meta-analyses of multiple studies and epidemiological research suggest that chronic low-carb diets (less than 40 percent of daily calories from carbs) are associated with higher mortality risks. (4)(5) 

    However, low-carb diets featuring minimally processed foods seem to be associated with lower mortality risks than low-carb diets featuring more processed foods. (6) So food quality — not just quantity — seems to matter a lot here.

    What Is the Keto Diet?

    Also known by its full name, the ketogenic diet, the keto diet generally dictates not having more than 20 to 50 grams of carbs each day, or less than 10 percent of your total daily caloric intake. (7) The idea behind triggering ketogenesis is losing weight by depleting glycogen stores and mobilizing increased amounts of fat stored in adipose tissue. (7)

    That idea, however, may not have a firm grounding. Research suggests that very low carb intake might not trigger ketogenesis, and might even hold health risks. (8)(9)

    Low-Fat Diet Vs. Low-Carb Diet for Overall Health

    First things first: how do these types of diets impact overall health factors? Let’s check out the research.

    Both types of diets are based on restricting one type of food (in this case, a particular macronutrient). Research suggests that restrictive eating habits — including being rigid about restricting certain types of foods — have been linked to the development and persistence of eating disorders. (10)

    Low-carb diets may be linked to developing long-term resistance to eating carbs and persistent feelings of guilt associated with any carb consumption. (11)(12) 

    Due to cultural stigma about fat — both dietary and body fat — low-fat diets may contribute to increased self-stigma and shaming regarding wanting and eating high-fat foods. (13) 

    These cultural associations also impact people’s development of disordered eating-related assumptions and negative beliefs about their own bodies vis a vis the foods they eat (or don’t eat). (14) Low-fat diets have also been associated with higher rates of depression in people with eating disorders.

    Low-Fat Diets for Overall Health

    Low-fat diets may help promote lower LDL (low-density lipoprotein) cholesterol levels, which may be desirable if you need to reduce your levels for medical reasons. (15)(16)(17) 

    Not all low-fat diets are extremely low in fat intake. But when you’re only getting 15 percent or less of your daily caloric intake from fats, you may be increasing your risk of metabolic syndrome. (18) Research suggests that these kinds of diets may be less likely to give you the baseline amount of energy and nutrients that you need to keep your body healthy. (18)

    Diets that are low in fat also may risk lowering immune function, especially when dietary fat levels are at 15 percent of daily calorie intake. (19) Raising intake levels to 32 percent may help mitigate the potential negative impacts on the immune system. (19) Athletes may also be at greater risk of too-low antioxidant levels when they’re on a chronically low-fat diet. (20)

    Low-Carb Diets for Overall Health

    Some studies have suggested that low-carb diets can result in increased HDL (high-density lipoprotein) and LDL levels. (21) But both low-carb and low-fat diets seem to have similar effects on cholesterol levels after 12 to 24 months of maintaining these dietary habits. (15)(16)(17) 

    More research is needed regarding the overall long-term effects of these diets, but it seems that initial differences between these diets may even out with time. (17) 

    A person checking their blood sugar level.Credit: / Shutterstock

    Reducing carbohydrate intake may improve glycemic control — a crucial component of diabetes management. (22)(7) However, research suggests that thinking about food more holistically than simply “carbs are bad” can help people manage diabetes with less risk of developing eating disorders. (23)

    Low-carb diets may also play a role in improving conditions as wide-ranging as acne and polycystic ovary syndrome to Alzheimer’s disease and non-alcoholic fatty liver disease. (24)(25)

    Low-Fat Diet Vs. Low-Carb Diet for Strength Training

    If you’re a strength athlete, you may think of your dietary habits in terms of their impact on your training. Here’s how low-fat and low-carb diets measure up against each other in the weight room.

    Low-Fat Diets for Strength Training

    There isn’t as much research focusing on low-fat diets impacting strength training as there is on low-carb diets and performance. That said, some research suggests that lower levels of dietary fat intake may negatively impact sports performance.

    While keeping total caloric intake the same, raising dietary fat levels to 42 percent can improve endurance during running and cycling. (26)

    Low-Carb Diets for Strength Training

    If you ask around your gym, many people might swear by keto diets that focus on very low-carb consumption habits. But low carbohydrate intake has been associated with reduced performance in high-intensity, short bursts of exercise like HIIT (high-intensity interval training) and high-intensity endurance training. (27)(28)(29) This makes sense, as you need carbs to fuel your body during tough workouts.

    Research suggests that your workouts might feel tougher — and your fatigue might be greater — when you’re following a low-carb diet. (30) In one study of CrossFit athletes, extremely low-carb (keto) diets were associated with a decrease in peak oxygen uptake and disruptions to hemoglobin levels. (31)

    CrossFitter taking a break to breathe.Credit: – Yuri A / Shutterstock

    That said, a study of elite weightlifters found that low-carb diets may help increase rapid weight loss without sacrificing performance over the course of three months. (32)

    Low-Fat Diet Vs. Low-Carb Diet for Weight Loss

    It’s easy to hear “low-fat diet” and think: fat loss. It’s also easy, given the dictates of diet culture, to hear “low-carb diet” and think: fat loss. Here’s what the science suggests.

    Low-Fat Diets for Weight Loss

    Since “fat” in general is often demonized in diet culture, low-fat diets are often associated with overall body fat loss. (33) But research suggests that low-fat diets are not more effective than other dietary strategies at promoting long-term weight loss. (34) 

    High-fat diets in weight loss intervention may actually be more effective at promoting weight loss than low-fat diet weight loss interventions. (34)

    Low-Carb Diets for Weight Loss

    One theory behind low-carb diets for fat loss is that when you lower your carb intake, you tend to increase protein and fat intake. 

    Protein especially promotes satiety — that feeling of being full. So you might wind up decreasing your total food intake since your hunger levels will be less likely to swing dramatically. (7) And sure enough, low-carb diets seem to increase athletes’ need for dietary protein. (35) So if you’re increasing protein intake along with low-carb diets, it might help promote weight loss.

    Many athletes believe that low-carb diets can help them lose weight because they see results so quickly from these diets. And while much of this weight may well be water loss, increased fat loss can also occur rapidly with low-carb diets. (7)(36) 

    However, around the year mark, weight loss seems to taper off and may even be reversed at around the same rate as other diets. (36) In other words, research suggests that low-carb diets may kickstart weight loss rapidly, but it doesn’t seem to be a sustainable choice after a few months to a year. (36) 

    Your Takeaways

    If you’re thinking about adopting a low-fat or low-carb diet, consider the potential impacts of both diets on your mental health and well-being. You might want to pay special attention to disordered eating habits and these diets’ relationships to body image and food stigma.

    When you’re weighing the potential pros and cons of either of these diets, consider:

    • Restrictive diets that involve avoiding particular foods or types of foods have been strongly associated with developing or reinforcing disordered eating habits.
    • Initial weight loss from these diets seems to taper off or even reverse after the year mark.
    • Very low-fat and low-carb diets may negatively impact immune health, peak oxygen uptake, metabolic syndrome risk, and athletic performance in the gym.

    You might consider a low-fat diet if you are:

    • Able to safely adopt a restriction-based diet.
    • Trying to lower your LDL levels and/or overall cholesterol levels.

    On the other hand, you may want to try a low-carb diet if you are:

    • Able to safely adopt a restriction-based diet.
    • Searching for ways to integrate more protein into your diet.
    • Trying to improve your glycemic control.
    • Aiming to potentially reduce the impacts of acne, non-alcoholic fatty liver disease, polycystic ovary syndrome, and Alzheimer’s.

    Low-Carb Vs. Low-Fat Diets — What to Eat?

    The sumo versus conventional deadlift. The low-bar squat versus the high-bar back squat. These rivals in strength sports go up against each other with similar gusto as low-carb diets versus low-fat diets.

    Since they’re both based on restriction, both diets have their risks for athletes who may be prone to developing disordered eating habits. They also both carry certain risks of athletes not getting the nutrients and other essentials that they need in their diets.

    But these diets also have the potential to decrease cholesterol levels and improve glycemic control. Choose your fighter if you feel able, and make sure you’re getting all your nutrients in. You’re going to need them to fuel your workouts.


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