Carbohydrate the muscle tissues post-exercise, because of GLUT4

Carbohydrate Backloading: A review

Carbohydrate Backloading
is a dieting strategy that was popularized by John Keifer. This strategy emphasizes
on keeping carbs at an absolute minimum throughout the day and ingesting
carbohydrates after the training session. 34

Mechanism of carbohydrate Backloading:

 It was hypothesized that carbohydrate backloading
takes advantage of the non-insulin mediated uptake of glucose by the muscle
tissues post-exercise, because of GLUT4 translocation, as opposed to in the
morning, when insulin sensitivity in both muscle and fat tissue is generally
higher 32.

Similar to GLUT (Glucose
Transporter) 1-3, GLUT4 and GLUT12 are a set of glucose transporters which are
present in muscle and fat tissue. While GLUT 1-3 are exposed to the cell surface,
GLUT4 are tucked below the surface within the cellular membranes. Due to this
withdrawn nature of GLUT4, this only reacts to the presence of insulin by
moving from the interior of the cell to its surface.  Thereby, this insulin-mediated transport of
glucose transports high volumes of glucose in the cells containing these GLUTs
(both muscle and fat tissue). 33, 34

However, resistance
training mimics the function of insulin in muscle cells and GLUT4 rises to the
surface shuttling glucose into the muscle tissue. This non-insulin mediated
uptake of glucose by the muscle tissues post-exercise is postulated to have
increases in the skeletal muscle tissue without any significant increases in
adipose tissue. 34

Research on carbohydrate backloading:

The most popular research
to support the theory of CBL is a 6 month study. In this study, Sofer et al. 35
authors compared the effects of carbs eaten mostly at dinner (experimental
group) vs. eaten throughout the day (control group) in a group of 78
Israeli police officers.  It was
found that reductions in weight, body fat and waist circumference were greater
in the evening-carb experimental group vs. the control group. In addition,
glucose control, inflammation, blood lipids and satiety were improved to a
greater degree in the evening-carb group.

However, there
are a few limitations to the design of the study. The subjects were fed a daily
average protein intake of 0.66-0.76 g/kg, which is much less than what
is consumed by resistance trainees aiming for a better body composition, which
questions the applicability of the research to this population. Also, the
experimental group lost an average 11.8 percent of their body weight in 6
months as compared to the control group who lost an average 10.9 percent, which
isn’t statistically significant (<1%) over 6 months. Also, the experimental group started at a greater weight to begin with. There are other controlled studies 36, 37 which were conducted, but no changes in body composition or weight loss were observed, however they were conducted for very short durations (15 days and 18 days). Summary Carbohydrate backloading doesn't provide any additional benefits in fat loss/ muscle gain when compared to a normal diet when calories and protein are equated. Though, in light of the limited evidence, it does seem that shifting caloric (and carbohydrate) intake to later in the day (around the training session) may provide a slight additional benefit with respect to body composition, better training performance and markers of health and disease.