Low Carb Diets: The Bad
Low-carbohydrate diets for weight loss, such as Atkins or Keto, have been receiving a lot of attention over the past decade. A low-carb diet focuses on foods high in protein and fat. Many types of low-carb diets exist, and each diet has varying limits on the type and amount of carbs you can eat. A typical low-carb diet limits the daily intake of carbohydrates to between 60 and 130 grams, while a ketogenic (keto) diet tends to stay below 30 grams of carbohydrates.
The re-emergence of low-carbohydrate diets into the spotlight has led many people to question whether carbohydrates are inherently 'bad' and should be limited in the diet.
If you remember back to our Back to Basics post on carbohydrates, the body uses carbs as its main energy source. During digestion, complex carbs are broken down into simple sugars, also called glucose, and released into your blood. This is called blood glucose. Insulin is released to help glucose enter the body's cells, where it can be used for energy. Extra glucose is stored in the liver and in muscles. Some is changed to body fat.A low-carb diet is meant to cause the body to burn stored fat for energy, which leads to weight loss. Weight loss can be a positive result of a low carb diet, but it’s important to recognize the many potential negative side effects that come along with following a low carb diet.
Low-Carb Diet Negative Side Effects
A moderate reduction in carbs (100 to 150 grams of carbs per day) probably isn't going to cause any noticeable side effects-If anything, you may feel a little fatigued for a few days. A larger reduction of between 50 and 100 grams of carbs could cause more pronounced effects. Severe carb limits can cause your body to break down fat into ketones for energy. This process is called ketosis. Ketosis can cause side effects such as bad breath, headache, fatigue and weakness.
The intensity of the side effects will depend on the following:
How much you reduce your carb intake
Your diet before you reduced your carb intake
Your individual sensitivity to the reduction in carbs
Headaches
If you are lowering carbs, you will also be reducing your sugar intake. Those who may be used to eating more sugar can lead to withdrawal symptoms like headaches. Studies show that headache severity increases when starting a low-carbohydrate diet.
Micronutrient Deficiencies
People who go on restrictive diets may not get all of the nutrients that they need. If you aren’t getting enough of certain micronutrients in your diet, specifically minerals, such as potassium and magnesium, you may experience muscle cramps. Potassium, sodium, and magnesium are responsible for muscle contraction and several other vital processes related to muscle and nerve function.
Additionally, people on a low-carb diet may not get enough of certain nutrients including thiamin, folate, vitamin C, magnesium, iron, vitamin D, vitamin E, vitamin B7 (biotin), fiber, and calcium. These are the most common nutrients that are likely to be deficient, but depending on the particular diet, there may be more.
When you lower carbohydrates, your body will carry less water due to how carbs interact with glycogen and water storage. Losing a lot of body water may also result in a loss of these minerals.
Bad Breath
Bad breath is an often-reported side effect of low carb diets. Sometimes bad breath is also combined with a foul taste in the mouth. On very low carbohydrate diets such as the keto diet, your body switches to ketones for fuel in the absence of preferred glycogen. These ketones are removed through urination and exhalation. The exhalation of ketones causes bad breath.
Reduced Athletic Performance
Low carbohydrate diets provide little in the way of glycogen energy stores- the body’s preferred source for fueling activity. You may notice a substantial drop in your ability to perform during exercise, sports, and training activities. Lower glycogen stores combines with a reduction in VO2 max (amount of oxygen measured in the body during exercise) can both lead to reduced athletic performance.
Constipation
While any change to your regular dietary patterns can cause alterations to your bathroom habits, constipation is a common complaint from those on a low carb diet, especially very low carb diets like keto.3
One reason for this is a lack of fiber due to minimal grains and beans, which are high-fiber foods but are also reasonably high in carbohydrates and so often avoided on low-carb diets.
While sometimes constipation can remedy itself as the body adjusts, keeping hydrated, taking a fiber supplement, or increasing low-carb, high-fiber foods in your diet can help.
Fatigue
Fatigue is a common symptom of low-carb diets because, as we know, carbohydrates are the body’s preferred fuel source. Limiting carbohydrates to amounts below what our body requires for optimal energy can lead to fatigue, especially as the body adapts to the new diet.
Low-calorie diets, in general, can also lead to fatigue, so be sure that you are not eating too few calories to support your energy needs. If weight loss is your goal, a caloric deficit is required, but one that is too extreme can have the opposite effect, reducing your total daily energy expenditure and slowing your metabolism.
The current research is not clear on possible long-term health risks a low-carb diet may pose. If you limit carbs in the long term, potential deficiencies in certain vitamins and/or minerals can cause irreparable damage. Additionally, some health experts believe that if you eat large amounts of fat and protein from animal sources, your risk of heart disease or certain cancers may go up. The research on this theory is mixed.
The Takeaway: A low-carbohydrate diet isn’t needed to lose weight and is not superior for weight loss to any other diet that creates a calorie deficit. Food quality and energy (calorie) balance is most important for healthy nutrition and weight management. Many people see weight loss on a low-carb diet not necessarily because of the carb restriction, but because a low carb diet forces them to take a look at their macros and generally pay more attention to the food they are eating. There are many negative side effects associated with eating a diet low in carbohydrates, so If you opt to follow a low-carb diet, be particularly mindful about the quality of foods you chose. A low- carb diet will also most likely negatively impact your athletic performance, which is important to keep in mind if you are trying to hit a backsquat PR or run a faster mile.