Every-Other-Day 'Fasting' in Trained Athletes: Effects Range from Fat Loss to Significant Performance Enhancement

ADF-esque diet strategy w/ dieting vs. fasting works for "athletes", too.

Intermittent fasting in its various incarnation (aka "lean gains" = 6/18, "every-other-day", "2-3 weekly fasting days, etc.) are getting more and more popular and science shows: #Fasting is probably not just a fad. In fact, the number of RCTs to confirm beneficial effects on body composition, inflammation, heart and brain health, etc. increases by the day. The latest addition to the accumulating research has just been published in the Journal of the ISSN; although, technically speaking it is rather an alternate days dieting regimen with a comparatively mild deficit of 33%.

In their paper, Victoria Pons et al. (2018) aimed to "evaluate the effects of every-other-day feeding CR interventions on the body composition and physical performance parameters (during maximal exercise tests) of well-trained athletes" (Pons 2018).
The scientists also estimate the possible impact of this CR intervention on the dietary deficiencies of micronutrients and essential fatty acids.

The study was a simple one-centre study with 12 (1 dropout) healthy male subjects. The inclusion criteria were: age (18–50 years old), sex (male), being a non-smoker, maintaining a balanced diet, and performing physical activity > 3 but < 6 days per week (yes, you can argue if those are "trained athletes", but that's pretty much the standard definition in studies). For the study, ...

"[...] participants carried out a CR of 30–40% with respect to their usual diet, on three alternate days per week for six weeks" (Pons 2018). 

Both, before and after the every-other-day fasting CR period, the participants took a maximal exercise stress test. For each participant, one blood sample was obtained at the beginning and another at end of the every-other-day fasting intervention at basal conditions and 30 min after acute maximal exercise.

What did the diet look like?

You've already learned that the subjects reduced their energy intake on the fasting days by 30-40%. The deficit was calculated for each participant by taking into account the individual’s resting metabolic rate, body weight, and physical activity per week.

Figure 1: Nutrient composition on unrestricted days (left) and intervention days (right | Pons 2018).

With an average calculated energy demand (mean ± sd) of 2351 ± 156 kcal/day (resting metabolic rate = 1862 ± 119 Kcal/day | physical activity of 3426 ± 1147 kcal/week), the energy content of the diet on fasting days was roughly 1500kcal/day - a deficit of 800kcal.

"The participants restricted their habitual diets for three alternate days each week and on the other four days participants’ dietary intakes were the same as they were at the beginning of the study without changes to caloric intake or distribution of meals" (Pons 2018).

Adherence to the nutritional intervention program was assessed using a 7-day dietary record during the last week of the intervention. All foods and fluids consumed, portion sizes, how foods were prepared, and how consumption habits were distributed throughout the day were recorded.

Based on the records, Victoria Pons et al. calculated that the subjects met their dieting goal of a -33% reduction in energy intake, ending up consuming an average of 1.537 ± 84 kcal/day; thus achieving a daily deficit of 814kcal/d on each of the three fasting days per week. Math tells us:

The cumulative weekly deficit was -2348kcal/wk - in theory!

In practice, the lack of strict dietary prescription on the non-fasting days gave the subjects enough leeway to compensate (or even overcompensate | learn more) for the lack of energy on the fasting days - leeway the subjects didn't use: In line with previous research showing that the issue of (over-)compensation in response to fasting is yet another of the die-hard diet myths, the scientists didn't observe changes in the subjects ad-libitum diet.

Figure 2: Relative change in energy and macronutrient intake during calorie restriction intervention (Pons 2018)

It is thus not surprising that the subjects lost a considerable amount of weight: 4.40% of their starting weight, to be precise - with weight loss occurring in the trunk (-6.4%), arms (-3.7%), and legs (-4.91%) weights.

As the researchers point out, "[body fat was the] main cause of body weight loss [while] lean body mass was only reduced by 2.91%" (Pons 2018). 

As a SuppVersity reader, you're now probably asking yourself how much of this weight loss was body fat... Well, relative to the total weight loss, the subjects lost sign. more body fat (-15.1% vs. -4.4%).

The detailed analysis of the DXA data the scientists collected before and after the intervention demonstrates that these reductions in body fat occurred mainly in the trunk (17.4%); the legs lost fat mass (10.4%) in a similar proportion to the arms (9.07%), but they lost the highest amount of lean mass (-3.47% vs. trunk and arms 2.45% and 2.62%, respectively).

Figure 3: Changes in body composition - total body (left, kg), arms, legs, trunk (right, grams | Pons 2018).

What cannot be overlooked in this context is the well-known and previously discussed influence of glycogen depletion/repletion on DXA-results. With a sign. decrease in total body water (TBW) from 45.4 ± 2.6 kg to 42.9 ± 3.6 kg after the CR intervention, and a shift of water from the intracellular to the extracellular domain, there's ample evidence that the loss of lean mass could be exaggerated due to limitations of the measuring technique. In fact, the differential analysis of the contribution of water loss reveals that...

"[t]he body weight losses induced by the 33% CR in well-trained athletes were mainly due to TBW losses, although extracellular water increased and intracellular water decreased their body content after the CR" (Pons 2018).

Since this would rather cause a false positive in terms of the loss of lean body mass, any potential measuring issues due to changing intra- and extracellular water levels wouldn't negate one of the most exciting results of the study:

Nutrient deficiencies may become a problem in the long-term

But there are other potential downsides of the fasting regimen - most prominently: nutrient deficiencies on the fasting days:

Vitamin A, B6, B12, C, E, Folate & Iron: Deficiency Nutrients in the US - 31% are Deficient | learn more

"The daily intake of magnesium, potassium, zinc, folic acid, and calciferol were about 60–77% lower than RDAs for athletes in the original unrestricted diet, and these values were reduced to 48–67% of RDAs with the CR. 

Additionally, the intervention significantly reduced daily intake of micronutrients and led to values lower than 90% of RDAs for iron, niacin, riboflavin, pyridoxine, and vitamins A and D" (Pons 2018).

This means that "[t]he CR diet created a situation of low micronutrient and vitamin intake, which, if maintained over the long term, could compromise athletic performance" (Pons 2018)... could.

"[Only o]ne-month 33% CR[, however,] did not compromise physical performance; on the contrary, it ameliorated several parameters related to physical performance" (Pons 2018) 

Now the bad news is that the effects the scientists call an "amelioration" are actually simple consequences of the lowered body weight and the metabolic downregulation. Together, they triggered a reduction in heart rates and energy expenditure required for running at 50%Vmax, 60%Vmax, and 70%Vmax and for running at threshold until exhaustion (-10%).

Figure 4: The sign. reduction in energy expenditure (kcal/min) during exercise at different intensities may be good news for endurance athletes, on the other hand, though, it partly explains weight loss plateaus in dieters (Pons 2018).

For athletes, this may really be an advantage, for people who are merely trying to lose weight/body fat, it will make making further progress even more difficult... and the increase in the relative contribution of fat to fuel the exercise (as evidenced by an ameliorated onset of the anaerobic phase of exercise with respect pre-intervention values), won't be a significant consultation for them.
References:

• Pons, Victoria et al. "Calorie restriction regime enhances physical performance of trained athletes." Journal of the International Society of Sports Nutrition 15:12 (2018).