High Protein Diets
The popularity of the Atkins diet has been astounding, in fact the book outsold the bible at times! However, research is now showing what many of us thought to be true - it's not all that healthy and isn't that good for fitness either.
High protein Vs high carb for cycling performance
7 subjects took part in this study which looked at the effects of a high protein diet on endurance cycling performance and compared it to the traditional high carbohydrate athletic diet (Macdermid & Stannard (2006) A Whey-Supplemented, High-Protein Diet Versus a High-Carbohydrate Diet: Effects on Endurance Cycling Performance. Interational Journal of Sports Nutrition & Exercise Metabolism; 2006;16:65-77).
Each subject took part in two 7-day trials in which they consumed either a high carbohydrate diet (7.9g/kg carbohydrate, 1.3g/kg protein) or a high protein diet (4.9g/kg carbohydrate, 3.3g/kg protein) - both diets were of the same calorie and fat content. On the 8th day of each trial period, the subjects cycled at a self-chosen pace for a body-weight dependent amount of work.
Results showed that performance during the trial on day 8 was significantly impaired following the high protein diet as compared to the high carbohydrate diet - performance of the required amount of work took an average of 153 minutes and 127 minutes respectively. This occurred despite no difference in physiological measures including HR and RPE throughout the trial.
Low carbohydrate diet may increase risk of bowel cancer
Recent research from the Rowett Research Institute in Aberdeen have suggested that low carbohydrate diets such as the Atkins diet may increase the risk of developing bowel cancer. (Duncan et al. 2007. Reduced Dietary Intake of Carbohydrates by Obese Subjects Results in Decreased Concentrations of Butyrate and Butyrate-Producing Bacteria in Feces. Applied and Environmetnal Microbiology,73(4);1073-1078). The researchers found that low carbohydrare diets lead to a reduction of the cancer-fighting chemical butyrate - an acid produced by bacteria which helps to kill off cancerous cells - in the gut.
In the study, 19 healthy, obese (BMI 30-42) subjects consumed a succession of either high, medium or low carbohydrate diets. The high carbohydrate dieters were consuming 400g/d carbohydrate - the average amount in a 'normal' diet - but the low carbohydrate group ate just 24g/d - the 'permissable' amount on a low carbohydrate diet. Those on the low carbohydrate diet experienced a 4-fold reduction in butyrate which could contribute to the development of bowel cancer in the future.