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Why Runners Should Avoid Restrictive Diets to Stay Fit

Many people try to follow some very strict diets (keto, low carb, paleo, low fat, low calories) to try to lose weight, look more fit. According to research, human beings cannot follow strict diets for a lifetime and stay healthy. People following strict diets, after a while, they will go back to their normal diet and gain more weight. One of the main side effects of restrictive diets is a lack of nutrients, which is a major issue for runners or athletes. All these restrictive diets will reduce the energy level, endurance, muscle health and recovery. Following a strict diet, missing some important nutrients, can decrease muscle refueling by 50%. Avoiding healthy carbs, healthy fats, not enough protein (plant-based or animal), not enough calories, will get our body depleted of many nutrients, vitamins and minerals. Runners need to focus on a healthy, balanced, personalized diet according to our body type, lifestyle, and training schedule and intensity. Some runners’ body might need more protein, more carbs, or more healthy fat than others. Eating a healthy diet with healthy and fresh foods, after some time, listening to our body and hunger, we will know which nutrients and how many calories our body needs for proper fueling to support our energy and recovery, muscle and bone health, and sleep pattern. Avoiding certain foods due to food allergy or sensitivity, we need to replace with foods that will provide the vitamins and minerals. Dairy-free diet might deplete the body of calcium, so we need to eat high-calcium foods -broccoli, cabbage, kale, almonds, chia seeds, beans, lentils, tofu, figs, which is even healthier than dairy. Gluten-free diet, the body will deplete the body of fiber, iron, and B vitamins. So to plan a nutrient, vitamin and mineral balanced diet will support runners and athletes, health, performance, and strength, also avoid some injuries.

Side Effects of Restrictive Diets

Low Carb Diet- A low carb diet is popular due to quick weight loss. Quick weight loss tends to be purely glycogen and the water it carries. As a regular runner, you can smash through your liver and muscle glycogen stores very quickly, glycogen depletion can cause many issues. With low levels or no glycogen, runners have no power source for energy as well as water for hydration. Yes you might start to burn fat, but that is a longer process since it burns much slower that carbohydrates. Your metabolism will start to be more sluggish, and a lot less energy for training.

High Protein Diet- As runners, we need to make sure we consume enough protein, the only negative issue is consuming too much animal protein and not enough fresh vegetables and fruits, it can lead to metabolic acidosis which is an imbalance of the body’s acid balance. The kidneys have to work overtime, which can cause kidney conditions and insulin resistance. We have to eat enough protein according to our training and exercises schedule, but to combine and balance animal and plant-based protein is much healthier. To follow a 80% plant-based diet and include small amounts of healthy fish or meat will support our overall health, such as cholesterol, heart and prevent many diseases such as diabetes or cancer. Plant-based diets are very healthy, but not every body type can support that diet.

Calorie Control Diet- Runners looking to lose weight and change their body shape focusing on calorie control will cause severe issues. Dealing with not consuming enough calories according to our daily calorie burning, will deplete our body of energy, nutrients, vitamins and minerals. The metabolism will shut down to survive, and once you start eating a bit more calories, the body will react by storing the calories and causing weight gain. Again, we need to follow a healthy, balanced personalized diet to keep the energy levels high enough.

Keto Diet- This type of diet will have many drawbacks for runners. Keto diet is high-fat, high animal protein and extremely low carbs, carbohydrate intake needs to be less than 50g per day. That means most runners’ favourite foods are mostly off limits:

  • Fruit

  • Legumes, lentils, beans

  • Bread and other whole-grain foods

  • Starchy vegetables like sweet potatoes, pumpkin, squash and beets

  • Alcohol

  • Many sauces and marinades that are high in sugar

And there are certain drawbacks. Potential side effects may include constipation, high cholesterol, acidosis, or kidney stones. According to research, runners who followed the keto diet consumed low levels of carbohydrates, and instead got most of their fuel from high-fat meals. Normal diets consisted of around 43 percent carbs and 38 percent fat. On the keto diet, runners only consumed 4 percent carbs and upped their fat intake to 78 percent. 

Researchers found that when the participants followed a keto diet and exercised at less than 60 percent of their VO2 max—the amount of oxygen can efficiently consumed and used—their exercise efficiency remained the same. 

But in exercise over 70 percent of VO2 max, their speed and endurance declined. In fact, running speed at VO2 max declined by 5 percent after keto-adaptation, once your body shifts from using carbs to using fat as the primary energy source.

This suggests that the keto diet would be just fine for moderate running efforts, but if you want to get faster, or workout at more intense levels, like powering up a hill, it may not be the best diet plan for your goals.

One reason? Fat is a less-efficient fuel source when you are exercising at high aerobic capacity. It requires more oxygen to create energy than carbohydrates do. Plus, the fatty acids are not as helpful in producing energy needed for muscle contraction, which may contribute to the loss of speed. And many people who followed a Keto diet, ended up with several health issues such as high cholesterol levels, heart issues, imbalanced hormone, and fatigue.

A diet cult is any diet that is based on the false idea that there’s a single ideal diet for humans. The underlying essence is that false belief that this diet (restrictive diet) is better than any other or even the only right way for anyone to eat. Eat healthy fresh foods, a nutrient balanced diet according to your body type and training, lots of vegetables, greens, fresh fruits, healthy fat and protein.

Macronutrient Intake Recommendation

Carbohydrate Intake Recommendation


1.2-2.0g protein/ kg bodyweight

Eat Healthy, Nutrients Balanced Meals, Fresh Foods, Lots of Veggies, Feel Great and Run Strong!


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