The pros and cons of a low carb diet
To carb or not to carb?
It's one of the most frequently asked questions by people wanting to lose weight. There's so much conflicting information surrounding carbs, so we want to clear the confusion with some science, and look at the pros and cons of low carb diets.
The science behind carbohydrates
First, we need to understand how our body uses fuel.
There are 3 types of ‘macronutrients' which provide our bodies with energy - carbohydrates, proteins and fats. Alcohol also yields energy, but unsurprisingly it's not essential to your body's functioning as the other macronutrients are. Carbohydrates and protein provide us with about 17kJ per gram, while fats provide us with about 37kJ per gram. In order to lose weight, for example, you need to consume fewer kilojoules than you are burning, no matter where these calories are coming from, carbs or otherwise. Therefore, weight loss is more about cutting calories than carbs. For a 1kg fat loss per week, you need to burn an extra 5000kJ per day (or consume 5000kJ less per day).
Ordinarily, your body will use a mix of carbohydrate and fat stores for energy. Carbohydrates are your body's preferred fuel, especially for your brain and your muscles. When your carbohydrate stores are running low and are not being topped up by your diet, your body will begin to use stored fat to fuel everyday processes and activity in a process called ketosis.
Pros of going low carb
- You can still eat great tasting high-fat foods such as butter, cream, mayonnaise, cheese, steaks etc., which are healthy in moderation
- Protein can help keep you feeling fuller for longer
- Low carbohydrate diets usually result in rapid weight loss due to the way in which water is stored alongside carbohydrate stores.
- Weight loss over a one-year period is comparable to a traditional low-fat diet.
- Some studies show an improvement in blood glucose control and insulin sensitivity.
- Some studies show an improvement in blood triglycerides levels and cholesterol levels but ONLY when saturated fat is also restricted
- Ketosis suppresses appetite
Cons of going low carb
- Carbohydrates are found in many different types of foods including bread and cereal, fruits and some vegetables and some dairy foods. Avoiding these food groups in order to reduce the total amount of carbohydrate will result in a sub-optimal intake of the vitamins and minerals found in these foods
- A lack of dietary carbohydrate can affect your mood and concentration
- Muscle loss is common, as the body looks to use protein for fuel. It can also lead to reduced exercise tolerance (from reduced glycogen stores in your muscle)
- Low carb diets are also generally low in fibre and antioxidants which can increase your risk of certain cancers, especially bowel cancer
- Low carb diets that advocate high protein can cause damage to your kidneys and bones
At the end of the day, it all comes down to controlling the total amount of calories that you are consuming, whether these come from carbs, fats or protein (or alcohol).
An ‘all-or-nothing' approach to carbs tends to be difficult to maintain long-term. Controlled portions of carbs and fats and proteins are the best way to ensure that you are not consuming too many calories, whilst still allowing you to have a balanced diet. For most people, this usually means moderately reducing carbohydrates, because most of us are out of touch with the amount of carbohydrate that constitutes a portion. As a general rule of thumb, a portion of carbohydrate-rich foods (pasta, rice, bread etc) is about the size of your fist (cooked).
Also ensuring that you choose foods that have a lower energy density is essential. That is foods that contain lots of vitamins and minerals without being too high in calories. This generally means choosing foods that are lower in fats and sugars and less processed foods. For carbohydrate foods, this would include wholegrain bread and cereals, beans and legumes, fruits and vegetables, and unsweetened low-fat dairy products. These will fill you up without adding extra unwanted kilojoules to help you achieve healthy long-term weight loss.
Written by Alex Porter
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