For many of us, the first week back at work after the long festive break is almost over. But, how many people have stuck to their New Year resolution to eat more healthily or follow the latest celebrity juice diet plan to lose weight? Many of us will have already given into temptation and broken our resolutions because most diet plans tend to focus on extreme kilocalorie restriction. With recent reports in the Lancet confirming that poor diet now contributes to a greater number of diseases than smoking, alcohol and a sedentary lifestyle combined, can one month of energy restriction (or one week in some cases!) really make a difference to overall, long term health?
It is generally agreed that diets focused on kilocalorie restriction work in the short term, however, there is less consensus about their longer term health effects and sustainability. One recent systematic review examined the efficacy of some of the most popular ‘fad’ diets. The study compared long and short-term weight loss across four diets. The review found that all diets were moderately effective for short-term weight loss but the loss was not sustained in the long- term (ie. more than 12 months). No diet was found to be superior for weight loss in either the short or long-term.
A further review published in the British Journal of Nutrition compared high-protein diets to low fat, high-carbohydrate diets. The study reported greater weight loss over 6 months in the high-protein diet, but all diet plans were equally effective over a 12 month period. The authors also found that the high-protein diet was lower in fruit and vegetable intake and may have implications for overall gut health.
In addition, energy restricting diets can result in weight gain once normal feeding begins, resulting in ‘weight cycling’. One systematic review reported that this was due to the physiological changes which occur during diet-induced weight loss. These changes encourage weight to be regained and might be an evolved survival mechanism to cope with periods of famine. These weight loss/gain cycles are reported to be extremely detrimental to health as they contribute to metabolic disease leading to increased mortality risk and poor cardiovascular outcomes.
The research suggests that fad diets are no substitute for a healthy lifestyle with regular physical activity. A recent NHS report states that dietary improvement not only promotes more sustainable weight loss, it can have significant improvements on metabolic health in both the short and long-term. Whilst the diet industry may promote kilocalorie restriction, these reviews agree that the advice should be to focus on good nutrition for weight loss and improved health outcomes. The benefits of making long term, sustainable changes to your diet and lifestyle and will go far beyond 2015.