Well, wouldn’t this be the dream…
Endurance athletes have the pursuit of improving power-weight ratio to make them faster, fatigue less and become more efficient. This can be done by either being lighter, improving power output, or both.
It’s been well establish that a calorie deficit is needed to drop body fat. Generally speaking, calorie deficits are associated with performance (and sometimes health) compromises.
As restricting calories is unfavourable for various performance markers, is there a way to drop body fat and weight by not restricting calories? This may be somewhat of a WTF question, but there’s some interesting research recently published by Moro et al (2020) to suggest you can.
Similarly to Intermittent fasting (IF), Time Restricted Feeding (TRF) controls the period of the day where you are allowed to eat. Unlike many IF protocols, TRF in this instance was used as a dietary maintenance protocol for 16 elite cyclist over a 4 week period.
The cyclists were divided into two groups; TRF and normal eating pattern. Both groups were instructed to eat 4800kcal per day (>700g carbs) that would theoretically not influence bodyweight or composition.
Each cyclist completed performance tests pre+post a typical pre-season training block (500km/week). The TRF group consumed 100% of their calories in an 8 hour eating window (10am-6pm), where the non-diet group consumed their calories between 7am-9p (normal).
Surprisingly, the TRF group dropped bodyweight and fat whilst preserving muscle tissue despite being at calorie maintenance. Interestingly, the non-diet group maintained body composition.
The researchers also measured some blood markers – of particular was a hormone called adiponectin. Low levels are associated with obesity and oxidative stress, where high levels are associated with increased resting metabolic rate (RMR). As the TRF group showed a 33% increase (vs 8% in non-diet), it was speculated that this contributed to fat loss.
Weirdly, RMR dropped in the TRF group and not in the non-diet group. Unsurprisingly, RMR reductions are usually associated with weight loss, but still conflict with the increased adiponectin levels. Pretty odd!?
More interestingly, TRF peak power output increased and by default, their Watts/kg further increased as a result of decreased body mass. Other performance measures such as VO2 max were maintained. Therefore, they significantly improved power-weight ratio.
Lastly, the TRF group showed improvements in certain immune markers and would suggest that this dieting approach could be more protective during the winter months.
Okay, so this all sounds fabulous… but there are some small elephants in each corner of the room:
1) Both groups were provided with meal plans to follow. Although reported adherence was good, I have my doubts. Under-reporting (lying) is a huge issue with nutrition based research and can impact the results greatly.
2) Did the TRF group actually do as they were prescribed? Eating 700g of carbs and 4800kcal in an 8 hour window is tough. I would speculate that the cyclists were not able to hit their calorie targets and ended up undereating, and therefore end up in a calorie deficit…which as we know is needed for fat loss.
Therefore, I would guess that the TRF group lost weight and body fat via a calorie deficit, as the non-diet group had extra time to consume food and actually ate at their true calorie maintenance.
If this was the case, it’s actually a pretty good way of dropping body fat – Eating to a point of complete satiety within a confined window where you’re unable to eat anymore and still be in a calorie deficit?
On the upside, you’ll also be eating a huge amount of carbohydrates surrounding sessions, therefore supporting performance, recovery and immune function.
I’m not going to rule out the fact that TRF could have some mystical powers of enhancing body composition, but for now, I think the latter is a more plausible explanation for why this happened…they were probably in a calorie deficit. Either way, the TRF group still got some pretty kick-ass results!
As this is a super new area of research, I feel that we’ll be revisiting this topic soon as new studies are published. For now, this is very much a ‘to be continued’…
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