Summer has now arrived, and for a lot of us it’s time for a quick shred before Christmas to get ourselves ready for the holidays! A lot of us will either decide to cut-out what we consider as ‘bad’ foods, or cut-down on our eating altogether. But do these strategies really work? We look at two popular diet choices – the low calorie diet, and the low-carb diet to find out.
The popularity of the low-carbohydrate diet originates from the Atkins Diet, introduced in the early 2000’s by nutritionist Robert Atkins. This diet involves limited consumption of carbohydrates, with a focus on proteins and fats. The aim is to bring the body into a state of ketosis - where the body’s metabolism switches from metabolizing glucose as energy, to converting stored body fat to energy. There is no calorie limit, meaning that eating is unrestricted, but dieters are advised to keep their carbohydrates limited to approximately 20g – 50g per day.
This diet became so popular that food companies had to introduce low-carb versions of their products. A major issue with this diet when it was first introduced was that many dieters overcompensated the carb restrictions by overeating meat, dairy and fats.
There is a widespread preference for low carb diets, as low carb diets are thought to promote a better body composition. Traditional calorie restricted diets result in weight loss, but this weight can include both fat and lean body mass (muscle!). Therefore a carb-restricted diet is increasingly popular to help preserve lean body mass. 
But does it work?
Research has shown that very low carb ketogenic diets result in greater weight loss and fat loss compared with low-fat diets in overweight men and women. A 2002 study involved twelve healthy normal-weight men switching from a 48% carb diet to a ketogenic diet of 12% carbs for 6 weeks. 8 men served as controls consuming a normal diet. There was a Fat mass decreased by 3.4 kg and lean body mass actually increased by 1.1kg after the ketogenic diet.
A 2009 study had a group of 800 overweight or obese people follow a diet for 2 years, with the diets consisting of different levels of protein, fat and carbohydrates. The study found that there was no effect on weight loss from diets with either a high or low carbohydrate level. 
However, all the diets involved reduced risk factors for cardiovascular disease and diabetes after 6 months and at the end of the 2 years. The high-carb diet decreased low-density lipoprotein cholesterol levels more than the lowest-carb diet.
The 5:2/Low Calorie:
The 5:2 diet became increasingly popular after it was televised in a BBC documentary written by journalist/presenter Michael Moseley. This diet encourages a type of intermittent fasting as well as calorie restrictions. For two days of the week, calories are limited to 500 calories for women and 600 for men, with unrestricted eating for the remaining 5 days.
This diet follows a traditional approach to weight loss, where one consumes less energy than they use. A major issue with the 5:2 is that dieters who found the two ‘fasting’ days very difficult, overate or binged during the unrestricted days. Another issue with this type of dieting is the potential harms. If one already has a diet poor in vitamins and protein, eating less food could lead to vitamin deficiency and muscle loss. 
There is research to suggest that a diet lower in calories can contribute to longevity. Residents of Okinawa, Japan, are known for a longer than average life expectancy, with high numbers of centenarians, and low risk of age-associated diseases. This has been related to the widespread healthy lifestyle in Okinawa, particularly the traditional diet, which is low in calories yet nutritionally dense.
A 2011 study with two groups of obese women found that patients receiving a low-calorie carbohydrate-restricted diet achieved larger weight loss than those on a conventional low-calorie diet. The subjects received a 1200 calorie diet with or without carbohydrate restriction for 1 week in hospital. This study, aiming to assess short-term effects, found a significant decrease in the weight of the subjects on carb restrictions, compared with those on calorie restrictions. 
So the verdict?
Long story short - what may work for some, may not work for all. What can be concluded with both diets is that regardless of how much you are consuming, the type of food you are consuming is more important. A low calorie diet can prove to be beneficial as long as one is still consuming a sufficient amount of nutrients, and low-carb diets do work for those who can ensure they do not overeat.
It is important to understand that both of the diets discussed above involve a major restriction, either in calorie intake or an entire food group. It is best to consider what is most suitable for your individual lifestyle and health condition before starting any diet program.
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