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:
1.
A variety of
whole grains that provide carbohydrates to fuel your workouts, in addition to
fiber and other vitamins and minerals
2.
Fruits and
vegetables that are full of vitamins, minerals, and antioxidants
3.
Lean protein
to help build and maintain your muscle mass
4.
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.
References:
1. Kiefer
J. Carb Back-Loading Manual for Total Body Fat Control. 1.0. John
Kiefer; 2012.
2. 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
3. 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
4. All About Cortisol. Precision Nutrition.
https://www.precisionnutrition.com/all-about-cortisol. Published March 2, 2009.
Accessed May 14, 2018.
5. 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
6. 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
7. 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
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