Burn the Fat: Carbohydrate Cycling for Fat Loss
If you ask most bodybuilders or competitors about carbohydrates, many will say that they stop eating carbs after 6 PM. In theory, it sounds logical that you would want to have lower levels of insulin at night, but the problem is there is no evidence to suggest that eating carbs past 6 PM leads to weight gain. In fact, some studies have found that eating carbs at night leads to enhanced fat loss.
One of the proponents of carbs at night has been John Kiefer and his Carb-backloading diet. The diet is based around ‘keep carbs low during the day and immediately after your evening workout, you eat carbs later in the evening.’
One of the most interesting aspects is carbohydrates’ ability to increase insulin which increases the metabolism stimulating the hormone leptin. Researchers from Israel thought that if the metabolism stimulating hormone leptin is high at night, which rise from eating a carbohydrate-enriched meal at night, while on a low calorie diet may cause a spike in insulin that may cause a greater increase in leptin which may lead to reduced appetite throughout the day.
Most competitors are hung up on the fact that carbs will raise the fat storage hormone insulin, but new research suggests that you should not get too hung up on worrying about insulin and be more concerned about the total macronutrient content of the diet. This isn’t going to be easy for low carb dieters to read this, but in a paper published August 13 in Cell Metabolism, titled, “Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity”, the researchers show how, contrary to popular claims, restricting dietary fat or low fat diets can lead to greater body fat loss than carb restriction, even though a low-carb diet reduced insulin and increased fat burning.
The researchers studied 19 non-diabetic men and women with obesity in the Metabolic Clinical Research Unit at the NIH Clinical Center in Bethesda, Maryland. Participants stayed in the unit 24 hours per day for two extended visits, eating the same food and doing the same activities. For the first five days of each visit, they were fed a baseline balanced diet. Then for six days, they were fed diets containing 30 percent fewer calories, achieved by cutting either only total carbs or total fat from the baseline diet, while eating the same amount of protein. They switched diets during the second visit. So basically they were placed on both a low carb and a low-fat diet with equal. The scientists used a mathematical model to predict long-term weight loss based on the subject’s responses to diets while they sat in a metabolic chamber.
So what happened at the end of the study? Daily energy expenditure decreased similarly on the low-carb diet and low-fat diets, but more weight was lost with low-fat diet vs. low-carb diet. Here is where it gets fascinating! Whole-body fat oxidation rapidly increased during the low-carb diet but was unchanged on the low-fat diet. In contrast, the low-fat diet demonstrated no change in fat oxidation despite reducing fat intake by ~800 kcal/day. While fat oxidation during prolonged low-fat and low-carb diets would be expected to decrease slowly over time, the researchers suggest the low-fat diet will lead to more long-term body fat loss than with the low-carb diet. At the end of the two dieting periods, the mathematical model proved to be correct. Body fat loss with dietary fat restriction was greater compared with carbohydrate restriction, even though more fat was burned with the low-carb diet.
However, over prolonged periods the model predicted that the body acts to minimize body fat differences between diets that are equal in calories but varying widely in their ratio of carbohydrate to fat. Carb restriction lowered production of the fat-regulating hormone insulin and increased fat burning as expected, whereas low-fat diets had no observed changes in insulin production or fat burning. These findings counter the theory that body fat loss necessarily requires decreasing insulin, thereby increasing the release of stored fat from fat tissue and increasing the amount of fat burned by the body. This is the first study to show that despite greater fat oxidation and lower insulin levels, low carb diets did not have greater weight loss than the low-fat dieters long term. The critical point to remember is that acute changes in hormones don’t necessarily always end up with measurable results.
Carbs Help You Recuperate During Intense Training
Few studies have investigated the effects of exercise training and carbohydrates on sleep physiology in well-trained athletes. The newest research conducted by investigators published in the Journal of Sport Sciences reported carbs help athletes sleep better at night. Researchers investigated changes in sleep markers, mood state and exercise performance in well-trained cyclists undergoing short-term intensified training and carbohydrate nutritional intervention. Thirteen highly-trained male cyclists participated in two 9-day periods of intensified training while undergoing a high or moderate carbohydrate dietary intervention before, during and after training sessions. Sleep was measured each night.
At the end of 9 days of intensive training, percentage sleep time fell during intensified training despite an increase in time in bed. Sleep efficiency decreased during intensified training. Actual sleep time was significantly higher in moderate than high carbohydrate diet throughout intensified training.
It is interesting to note that actual sleep time was significantly greater during intensified training in moderate than high carbohydrate diet, which may indicate an increased requirement for recovery and/or expression of fatigue. It was also observed that during the intensive training, heart rate was significantly greater in moderate than during the high carbohydrate diet. This could indicate a higher level of fatigue in the moderate carbohydrate condition and that high carbohydrate diet may have provided a level of protection a against the changes in sympathetic nervous activity that are thought to be linked to the overtraining that occurs with intense, consecutive training. Mood disturbance increased during intensified training and was higher in moderate than high carbohydrate diet. The main findings of this study were that 9-days of increased training in highly-trained cyclists resulted in significant and progressive declines in sleep quality, mood state, and maximal exercise performance.
Carbohydrates are not the evil food that we once thought they were and many athletes who are training hard can benefit from carbohydrates from their diet. The key is to measure your macronutrients depending on your goals, whether it be fat loss or muscle mass.
Cell Metabolism, Hall et al.: “Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity” http://dx.doi.org/10.1016/j.cmet.2015.07.021
Sofer, Sigal, et al. “Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner.” Obesity 19.10 (2011): 2006-2014.
Sofer, S., et al. “Changes in daily leptin, ghrelin and adiponectin profiles following a diet with carbohydrates eaten at dinner in obese subjects.” Nutrition, Metabolism and Cardiovascular Diseases 23.8 (2013): 744-750.
Killer SC, Svendsen IS, Jeukendrup AE, Gleeson M. Evidence of disturbed sleep and mood state in well-trained athletes during short-term intensified training with and without a high carbohydrate nutritional intervention. J Sports Sci. Sep 25:1-9.