Nutrition

Is a Low Carb Diet the Best for Weight Loss?

When it comes to losing weight, many diets come down the same message — severely cutting carbs, and often eating more fats. This typically includes cutting out foods that we tend to eat too much of, such as sweets, pasta, and bread. This generally can quite easily lead to weight loss, but is it the only way?

 

What Do Carbs Do?

Carbohydrates are the body’s primary fuel source. They break down into energy for our brain, lungs, muscles, and other cells. They’re especially crucial for high-intensity exercise, when we push our muscles to the max. Carbs travel through our blood stream after digestion (known as “blood sugar”). Our body produces insulin, which directs the sugar to the cells for energy or for storage (when we get more than we need).

pasta

 

What is a low-carb diet?

A low-carb diet is exactly what it says on the tin. You cut your carbohydrates down to make up a much smaller proportion of your daily macronutrients (protein, carbohydrates, and fats). This can include foods such as fruit depending on how strict the low carb diet is. The idea is that by cutting out carbs, you’ll be cutting out excess calories.

 

Why are carbs bad when trying to lose weight?

Carbs can be “bad” when trying to lose weight if you typically overeat high-carb foods. This is often the case, when we consume pasta, pizza and desserts in addition to healthier high carb foods — like fruits, whole grains, and dairy products. Many research studies have proven that low-carb diets can work because they simply reduce total calorie intake.1 However, both low-carb/high-fat diets and low-fat/high-carb diets can be equally successful, as long as they both reduce total calorie intake.2

 

Low Carb vs. Low Fat for Fat Loss

Although you probably have friends and family members who swear by one approach or the other, the science shows that they can be equally effective for weight loss, as long as you burn more calories than you consume from food.2

Low fat diets have been popular for a long time, as fat is higher in calories (9 per gram) than carbohydrates or protein (4 per gram). Because high-fat foods are typically high in calories (fried foods, oils, etc.), reducing intake of these foods is an easy way to reduce overall calorie intake. Low-fat diets are also regarded as being more heart healthy, as they’re lower in cholesterol and saturated fats.

While carbs are lower in calories per gram than fat, portions of carb-rich foods are usually large and easy to overconsume since they aren’t as filling and satisfying as higher fat or protein foods. Fat slows down digestion and keeps food in your stomach longer, sending signals of fullness to your brain. Protein acts in a similar way to make you feel full and satisfied, which is why people who following a high-fat, high-protein, low-carb diet can be successful in reducing total caloric intake.

 

How Do Low Carb Diets Work?

Carbs are the main source of glucose, which is the basic fuel for the brain (and the rest of the body) runs on. When carbs are kept to a minimum in your diet, your body needs to find alternative energy sources and starts to break down fat for energy instead. Typically, you consume more protein and fat when you reduce the carbs in your diet. Depending on the specific type of diet you’re following, you might eliminate fruit and starchy vegetables or just eat them in smaller portions, less often.

healthy carbohydrates

 

Benefits of a Low-Carb Diet

Struggle to stick to that diet? Studies have shown that a low-carb diet reduces your appetite. It’s thought that because you’re eating more protein and fats, you fill up quicker, but still end up eating less calories.3

You’re also likely to lose more weight than on other diets to begin with. That’s because your body work to get rid of that excess water from your body, meaning bigger losses in the first week or two.4

There’s also an increase in good HDL cholesterol on a low-carb diet as it encourages you to eat more healthy fats to replace some of the calories you’re not eating from carbs.5

 

Risks of a Low-Carb Diet

Low levels of sodium can be common on a low-carb diet. This is because your insulin levels drop on a low-carb diet, so your body starts getting rid of sodium along with water. Sodium’s an important electrolyte and if levels drop too low, then you can suffer from dizziness, fatigue, and headaches.

 

Popular Low Carb Diets

Keto

The Keto diet emphasises a high fat, very low (or no) carb eating pattern. When your body isn’t getting any carbohydrates (and not too much protein) from food, it starts to break down fat stores for energy — a process called ketosis. This process produces ketones, which are an alternative source of energy for your brain to use instead of glucose.

Staying in this metabolic ketosis state can be difficult, as your body will switch back to burning glucose when you do consume too many carbs. Also, all of that fat you’re eating will be stored if you switch back to carbs (which can sabotage your weight loss). Although this diet is very popular and can lead to fast results, it can be difficult for some people to stick to long term.

Atkins Diet

The Atkins Diet is another popular low carb eating pattern that focuses on high-protein and high-fat foods, but it’s split in to “phases” that help you slowly reintroduce certain “healthy” carbohydrates in small portions once you attain the weight loss you desire. It’s less strict than the Keto diet and does allow some carbohydrates eventually, whereas the Keto diet eliminates them to keep the body in the fat-burning state.

South Beach Diet

Similar to the Atkins Diet, the South Beach Diet is a low carb eating plan that’s broken into phases that slowly reintroduce a low level of carbohydrates for long-term maintenance. The main difference from the Atkins or Keto diet is that it emphasizes low-fat meats and heart-healthy fats.

 

The effects of a low-carbohydrate intake on exercise

While a low-carb diet can be an easy choice for losing weight, how does it impact performance when our muscles depend on it for energy? Refuelling after a workout should be focused on two things — replenishing glycogen in the muscles (the stored form of carbohydrate) and protein for repair and growth. After an intense workout, our muscles are depleted of their energy stores (called glycogen), and rely on carbs from our diet to rebuild those stores before we exercise again.

Two key factors for athletes to consider are the total carb intake for the day and the timing of their carbohydrates.6 It’s crucial to consume easily digested carbohydrates soon after a challenging workout to help your body recover and rebuild stores of glycogen. While some people can train well on a low-carb diet, others might experience a drop in performance if they are used to having more carbs and suddenly cut them out.6

Some athletes practice “carb cycling” for performance. This means alternating days of higher carb intake with days of lower carb intake, planned around your workouts and recovery periods. This is one way to try a lower carb eating pattern while still fuelling your body for more intense workouts when necessary. Although it follows the principles of a low carb diet while also considering the need for glucose for recovery, there’s limited scientific evidence or guidelines published on carb cycling. It may take some trial and error to get an alternating low carb/high carb eating pattern to give the results you’re looking for.

 

Diet Plan and Tips

Low-carb diet plans vary greatly and should be adjusted based on your health, how much weight you have to lose, and how much you exercise. There are many low-carb prepared foods on the market, like cauliflower pizza crust and low-carb breads. However, it’s just as easy to choose healthy, whole foods. If you want to try a low-carb diet for weight loss, here are some general ideas of the foods you should include and some to avoid.

What to eat on a low-carb meal plan

Low-carb foods (eat often): meat, eggs, chicken, turkey, fish, green vegetables, nuts, seeds.

Moderate carb foods: dairy products (milk, yogurt), beans, some gluten free grains (quinoa, millet), some fruits, certain starchy vegetables (peas, sweet potatoes)

 

Foods to avoid:

High-carb foods (avoid): sugary foods (desserts, baked goods, soda, juices), pastas, breads, rice, noodles, potatoes, corn, cereals, low fat “diet” foods (often high in carbs).

Depending on the type of low-carb diet plan you choose to follow, you may include, exclude, or limit any of the moderate carb foods as well. Here are three low-carb examples for each meal of the day (and snacks).

Drinks to avoid:

Alcoholic drinks such as beer tend to have quite a high carb content because starch is one of the main ingredients. That doesn’t mean you should swap for a cocktail either, though, as fizzy drinks and juice are often high in sugar, and therefore carbs.

beer is a drink to avoid on a low carb diet for weight loss

 

Low-carb meal plan

Breakfast:

Omelette with cheese, diced peppers and onions

Cottage cheese with peanut butter

Scrambled eggs with spinach and bacon

Lunch:

Turkey- or ham and cheese roll-ups and cucumbers

Spiralled courgette noodles (or spaghetti squash) with alfredo sauce and coleslaw

Tuna salad with mayo on baby greens

Dinner:

Grilled chicken with sautéed mushrooms and asparagus

Salmon, cauliflower “rice” and stir-fry veggies

Bacon cheeseburger (no bun) with roasted vegetables

Snacks:

Celery with peanut butter

Tomatoes with mozzarella cheese, topped with olive oil and balsamic vinegar

Kale chips with mashed avocado

 

Why your low-carb diet might not be working

Been eating barely any carbs and still not losing those extra inches? Just because you’ve cut carbs doesn’t mean you’ll automatically lose weight. If you’re replacing the calories lost from the lack of carbs with more protein or fat, then you could end up putting on weight instead of losing it.

To lose weight, you need to be in a calorie deficit, which means eating less calories than you burn in a day. So, if you cut out 100 kcal of carbs, but then replace that with 100 kcal of protein, then you won’t be in a calorie deficit and lose weight.

For a low-carb diet to succeed, you need to cut down your carbs, but not eat those extra calories from other food groups.

 

Take Home Message

Low-carb diets are a popular and easy way to lose weight. They work by limiting food choices and leading to an overall reduction in calorie intake. Some diet plans restrict entire food groups while others reintroduce carbohydrates once you meet your weight loss goal. However, carbs are a crucial part of the recovery process and can impact performance for some athletes when cut too low. There are many different types of low-carb diets, and it’s important to consider your goals and lifestyle when choosing the right diet for you.

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Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.


  1. Astrup, A., & Hjorth, M. F. (2017). Low-fat or low carb for weight loss? It depends on your glucose metabolism. EBioMedicine, 22, 20-21.
  2. Gardner, C. D., Trepanowski, J. F., Del Gobbo, L. C., Hauser, M. E., Rigdon, J., Ioannidis, J. P., … & King, A. C. (2018). Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: the DIETFITS randomized clinical trial. Jama, 319(7), 667-679.
  3. McClernon, F. J., Yancy Jr, W. S., Eberstein, J. A., Atkins, R. C., & Westman, E. C. (2007). The effects of a low‐carbohydrate ketogenic diet and a low‐fat diet on mood, hunger, and other self‐reported symptoms. Obesity15(1), 182-182.
  4. Volek, J. S., & Westman, E. C. (2002). Very-low-carbohydrate weight-loss diets revisited. Cleveland Clinic journal of medicine69(11), 849-853.
  5. Foster, G. D., Wyatt, H. R., Hill, J. O., McGuckin, B. G., Brill, C., Mohammed, B. S., … & Klein, S. (2003). A randomized trial of a low-carbohydrate diet for obesity. New England Journal of Medicine348(21), 2082-2090.
  6. Burke, L. M., Hawley, J. A., Wong, S. H., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of sports sciences29(sup1), S17-S27.

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Claire Muszalski

Claire Muszalski

Registered Dietitian

Claire is a Registered Dietitian through the Academy of Nutrition and Dietetics and a board-certified Health and Wellness Coach through the International Consortium for Health and Wellness Coaching. She has a Bachelor of Science in Biology and a Master’s degree in Clinical Dietetics and Nutrition from the University of Pittsburgh.

Talking and writing about food and fitness is at the heart of Claire’s ethos as she loves to use her experience to help others meet their health and wellness goals.

Claire is also a certified indoor cycling instructor and loves the mental and physical boost she gets from regular runs and yoga classes. When she’s not keeping fit herself, she’s cheering on her hometown’s sports teams in Pittsburgh, or cooking for her family in the kitchen.

Find out more about Claire’s experience here.


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