Submitted by Amy Sercel MS RD CD
Edited by Marcia Bristow MS RDN CSSD CD
In the world of nutrition news, the topic of carbohydrates is one of the most confusing and controversial you’ll find right now. Depending on the source, the recommendations range from entirely avoiding all carbohydrates to limiting yourself to certain types but not others. If you’re following the trends, you might have heard about carbohydrate back-loading for losing weight and preserving muscle mass. In regards to this blog, I am reminded of a quote I once read, “Be careful what you read, you might die of a misprint someday!” Regardless, here is the information on Carb Back-Loading.
Carbohydrate back-loading is detailed in a book by John Kiefer, a “training and nutrition consultant” whose qualifications include having “read over 40,000 medical research papers covering various facets of human biology.”1 In short, Kiefer advises to avoid eating any carbohydrates until immediately after an evening workout that focuses on resistance exercise. After the workout, you should eat large quantities of carbohydrates, especially “junk” carbohydrates because they have a higher glycemic index and will be more readily absorbed into your muscles.1
Foods like white bread, potatoes, candy, and sugar-sweetened drinks are said to have a high glycemic index because they raise your blood sugar quickly after you eat them. Foods with a low glycemic index contain a mix of carbohydrates, protein, fat, and fiber, and will cause your blood sugar to rise slowly and stay more even over time. Kiefer actually says to avoid carbohydrates with a low glycemic index after a workout. He says they will create a prolonged increase in blood sugar levels, which will prevent your body from releasing growth hormone while you sleep and therefore limit the amount of lean tissue building that would occur overnight. On the other hand, he argues, the blood sugar crash that occurs after eating high glycemic index foods will ensure that your overnight growth hormone release will be normal.1 The problem with this theory is that blood sugar levels still remain high several hours after finishing a high glycemic index meal, and blood sugar may even return to normal more quickly after eating a meal that contains more fiber and protein, and thus has a lower glycemic index.2
Kiefer also claims that your cells are most insulin-sensitive in the morning, so when you eat carbohydrates at this time your body quickly stores them in both your muscle and fat cells. He says that skipping breakfast and avoiding carbohydrates during the day will promote fat burning by preventing your body from storing calories in fat cells, and by allowing another hormone, cortisol, to stimulate fat breakdown. When you do eat during the day, he recommends continuing to avoid carbohydrates, instead focusing on lean meat and low-carbohydrate vegetables like asparagus, spinach, broccoli, cauliflower, cabbage, zucchini, and bell peppers.1
With this argument, Kiefer is overlooking a few essential points about the cortisol. Cortisol is a stress hormone that’s released when the body needs energy. It does trigger the breakdown of fat stores, but it also stimulates the breakdown of muscle to be used as energy. Eating carbohydrates prevents muscle breakdown because the body uses those carbohydrates for energy first. Kiefer also implies that muscle protein breakdown doesn’t happen unless cortisol is “constantly elevated like during chronic stress,”1 however, this is untrue. Cortisol acts on all cells, and doesn’t distinguish between fat and muscle when converting stored fuel into usable energy. Additionally, to ensure that there is plenty of fuel in the bloodstream cortisol actually increases your appetite, which would make it much more difficult to avoid eating during the first half of the day.3,4
Kiefer’s final major argument is that you should do resistance training at night because resistance training makes your muscle cells able to absorb carbohydrates without needing insulin. Since your other cells are least insulin sensitive at night, waiting to eat carbohydrates until after a resistance workout would ensure that those carbohydrates are stored only in muscle. While he does include protein-rich foods in the post-workout meal, he only highlights the importance of eating carbohydrates to replenish muscle glycogen stores to prepare for the next workout. Training earlier in the day wouldn’t have the same impact, because your cells would be more sensitive to insulin and you would end up storing carbohydrates in both your muscle and fat.1
In addition to the factual inaccuracies scattered throughout Kiefer’s argument, the entire theory of carbohydrate back-loading goes against most nutritional biochemistry knowledge. To begin with, once the body has reached its capacity for carbohydrate storage in the muscles, liver, and kidneys, any additional carbohydrates eaten will be stored as fat no matter when those carbohydrates are eaten, or if they are high or low glycemic index foods. This means that even after a tough resistance workout, people still need to be conscious of the amount of calories they take in to prevent those calories to be stored as fat. Furthermore, insulin will still be released when you eat carbohydrate-rich foods after a workout. It’s possible that your muscle cells would take in more of the carbohydrates than your fat cells at this time, but there is no way to simply “turn off” the storage of carbohydrates in fat.
At the same time, there are many studies that directly oppose the idea that you should eat all of your carbohydrates at night. One study in particular showed that dietary-induced thermogenesis, or the number of calories burned by digesting food, was higher when the majority of food was eaten in the first half of the day, and people eating larger morning meals lost almost twice as much weight during the course of the study than those who ate larger evening meals.5 Another study suggests that people who eat a high-carbohydrate breakfast every day are more likely to maintain weight loss and less likely to experience food cravings throughout the day.6
Throughout the book Kiefer takes an aggressive tone that seems to imply that anyone who questions his plan simply doesn’t have enough discipline. He tells condescending stories about people who have “incorrectly” followed his carbohydrate back-loading plan, belittling the efforts that they did make without offering any suggestions for how they could make the plan effective for their lifestyles. It’s well known that the mindset of being either “on” or “off” of a diet actually has worse health outcomes than creating sustainable lifestyle changes that fit within a person’s preferences. The type of dichotomous thinking that Kiefer encourages ultimately leads to more weight gain, less enjoyment of food and eating, and can even trigger an eating disorder in someone who is predisposed to developing one.7
All in all, carbohydrate back-loading is an interesting idea that is ultimately not backed up by nutrition science. Instead of trying to follow a restrictive eating pattern developed by someone whose main credential is having read research studies, listen to the recommendations that are known to be true. Focus on creating a balanced meal pattern that allows you to feel satisfied and enjoy the meals you’re eating while staying within your calorie and macronutrient needs. That meal pattern will include:
- A variety of whole grains that provide carbohydrates to fuel your workouts, in addition to fiber and other vitamins and minerals
- Fruits and vegetables that are full of vitamins, minerals, and antioxidants
- Lean protein to help build and maintain your muscle mass
- Fish, nuts, avocados, olive oil, or other unsaturated fat as sources of healthy fat
Keep in mind, you can always seek out a Registered Dietitian to provide you with individualized recommendations tailored to your lifestyle to ensure that you’re meeting your unique needs as best as possible. After all, just because a program or plan works for one person does not necessarily mean it will work for you.
- Kiefer J. Carb Back-Loading Manual for Total Body Fat Control. 1.0. John Kiefer; 2012.
- Yalçın T, Al A, Rakıcıoğlu N. The effects of meal glycemic load on blood glucose levels of adults with different body mass indexes. Indian J Endocrinol Metab. 2017;21(1):71-75. doi:10.4103/2230-8210.195995
- Christiansen JJ, Djurhuus CB, Gravholt CH, et al. Effects of Cortisol on Carbohydrate, Lipid, and Protein Metabolism: Studies of Acute Cortisol Withdrawal in Adrenocortical Failure. J Clin Endocrinol Metab. 2007;92(9):3553-3559. doi:10.1210/jc.2007-0445
- All About Cortisol. Precision Nutrition. https://www.precisionnutrition.com/all-about-cortisol. Published March 2, 2009. Accessed May 14, 2018.
- Raynor HA, Li F, Cardoso C. Daily pattern of energy distribution and weight loss. Physiol Behav. February 2018. doi:10.1016/j.physbeh.2018.02.036
- Jakubowicz D, Froy O, Wainstein J, Boaz M. Meal timing and composition influence ghrelin levels, appetite scores and weight loss maintenance in overweight and obese adults. Steroids. 2012;77(4):323-331. doi:10.1016/j.steroids.2011.12.006
- Palascha A, van Kleef E, van Trijp HCM. How does thinking in Black and White terms relate to eating behavior and weight regain? J Health Psychol. 2015;20(5):638-648. doi:10.1177/1359105315573440