With all the Google Education and exposure, by this time we all are very much aware of “What are carbohydrates and why they are important?” But just to follow the protocol, I will start the article with brief introduction of carbohydrates.
Carbohydrates, Types and Function
Carbohydrates are energy giving nutrients made up of oxygen, hydrogen and carbon atoms. It is transformed into glucose to provide energy and the extra ones are stored in the form of glycogen and fats.
There are two types of carbohydrates
1. Simple ((provides instant energy) &
2. Complex (provides slow and steady energy)
Apart from providing energy carbohydrates also spare protein to maintain lean body mass.
Low carbohydrate diet
A low-carb diet limits carbohydrates — such as those found in grains, starchy vegetables and fruit. Low-carbohydrate diets for weight loss are receiving a lot of attention of late. Reasons for this interest include, low-carbohydrate diet books, the over-sensationalism of these diets in the media and by celebrities, and the promotion of these diets in fitness centres and health clubs. The re-emergence of low-carbohydrate diets into the spotlight has lead many people to question whether carbohydrates are inherently ‘bad’ and should be limited in the diet. However, abundance of evidences has shown that low-carbohydrate diets present no significant advantage over more traditional energy restricted, nutritionally balanced diets both in terms of weight loss and weight maintenance.
There are many variations on just what a ‘low-carbohydrate’ diet is. Some popular diet books such as Dr. Atkins’ Diet Revolution, The Carbohydrate Addict’s Diet, Protein Power and Sugar Busters, have common recommendations in that they advise consuming protein as the primary macronutrient for the body, with the remainder of the energy to be made up from fat.
Weight loss achieved on low-carbohydrate diets..
In an experiment 18 subjects who followed low carbohydrate diet lost 7.7 kg in 8 weeks. The dietary protocol represented an average kilocalorie restriction of approximately 1123 kilocalories/d relative to the subjects’ average previous diet. The dieters lost on average 3.6 kg in the first two-week induction period. In the following three two-week periods, weight loss was in the order of 1.4 kg per fortnight. The results showed that weight loss was entirely due to energy restriction achieved through a decrease in carbohydrate consumption by 90% while the actual amounts of fat and protein eaten changed little compared to the habitual intake of the participants prior to the commencement of the diet.
The US National Weight Control Registry, which compiles details of individuals who have lost more than 13 kg for a year or more, analysed the diets of 2681 members. They found that less than 1% of these successful people had followed a diet classified as ‘low carbohydrate’ (defined as 24% or less total daily kilocalories coming from carbohydrate) as maximum found low carbohydrate diet as difficult and unrealistic. Further to this, a study analysing the diets of over 10,000 free-living adults found that those individuals consuming a diet with 55% of energy from carbohydrates, compared to those whose diets comprised zero to 30% energy contribution from carbohydrates, actually ate the same amount of food in terms of weight (2,271 ± 21g versus 2,225 ± 103g), however consumed less energy, more fibre and less fat.
Such data suggests that a high-carbohydrate diet, which contains unrefined grains, cereals, nuts and legumes, and plenty of fibrous matter is more nutritionally adequate and can bring sustainable weight loss than low carbohydrate diets or any other fad diets.
Short term health implications
One of the common metabolic changes seen when a person follows a low-carbohydrate diet is ketosis. When dietary carbohydrates are in limited supply, the body will utilise its reserves of glycogen in order to meet glucose demands. Glycogen stores in the body are quite small with approximately 70-100 g in the liver and 400 g in muscle. Most of these glycogen stores are exhausted within 24 to 48 h of carbohydrate restriction. As each gram of glycogen is bound with 3g of water, then a simple calculation shows that a ‘weight loss’ of around 1- 2kg can be achieved within the first week of the diet, resulted due to water loss and not due to the burning of fat stores. Loss of glycogen and water is not a true measure of weight loss as glycogen and water stores will be replenished once the diet ends.
All hypoenergetic diets result in loss of body weight and body fat. Losses of protein and fat are the same during a ketogenic diet as during a hypoenergetic non-ketogenic diet. Hence no diet is superior to another in terms of preservation of lean body mass. However, low carbohydrate diets are at greater risk of being nutritionally inadequate as they enforce restriction of food choices. Typically, low-carbohydrate diets are low in fibre, thiamine, folate, vitamins A, E, and B6, calcium, magnesium, iron, and potassium. Low-carbohydrate diets are also usually higher in saturated fat and cholesterol with protein mainly being derived from animal sources. Comparison of a range of popular diets revealed that low carbohydrate diets (defined as less than 30% of energy from carbohydrate) fared worse in terms of dietary adequacy while high-carbohydrate diets (defined as greater than 55% of energy from carbohydrates) gave the highest dietary adequacy score. The dietary rating, known as the Healthy Eating Index (HEI) gives a score of 82.9 which was the highest score recorded for the range of diets analysed while low carbohydrate diets received a score of 44.6 (the lowest recorded score in the study).
Physical Activity
As an increase in physical activity is often undertaken in conjunction with weight loss, the influence of carbohydrate restriction on physical performance is an important issue to examine.
A low carbohydrate intake over a period of three to four days results in metabolic acidosis due to increased circulation of free fatty acids. It has been seen that the presence of metabolic acidosis may be a factor in leading to fatigue. An average untrained individuals, have a diminished fat oxidative capacity hence have a greater reliance on glucose as fuel source during exercise. Taking these findings into consideration, it can be easily concluded that carbohydrate restriction on an inactive, untrained and overweight person may compromise weight loss due to impairment of the ability to exercise at the individual’s maximum capacity.
Bone Health
In terms of weight loss, the simple fact of energy balance cannot be ignored; any diet that is hypoenergetic will result in weight loss. When using loss of body fat as a true measure of weight loss, then low-carbohydrate diets gets no extra points over nutritionally balanced, hypoenergetic diets. Based on the available evidence, long-term compliance to a low-carbohydrate diet may put an individual at greater risk of an array of metabolic diseases without the achievement of sustainable weight loss.
Practical advice for sustainable weight loss
The use of the ketogenic diet in people with cancer is one controversial topic. According to the theory, the nutritional ketosis caused by a ketogenic diet could cause oxidative stress in cancer cells but not in healthy cells. Experiments in animals have shown that the ketogenic diet is effective against the metastasis (spread in different parts of the body) of cancer. Specific case studies for certain cancers have shown some evidence of cancer regression.
Conclusion
With the rising tide of obesity, the lure of easily attainable weight loss by following a low-carbohydrate diet is certainly appealing. People have become completely obsessed with weight loss and have started holding a belief that ‘As long as I lose weight I don’t care what I have to do and what could be the future sufferings’.
To conclude, before adopting any diet for weight loss one should introspect the mistake that has resulted obesity. It could be overeating, over indulgence in fats, an inactive lifestyle, any medical condition or may be all the four. Correcting these mistakes and adopting a hypoenergetic, healthy diet which is a good combination of all the macronutrients, fibre, water, vitamins and minerals can only bring sustainable weight loss with good health and can also encounter lifestyle diseases such as diabetes, fatty liver, high blood pressure and many more.
