If you’re an intermittent fasting/time-restricted feeding enthusiast or proponent, you may have heard about a recent study that took the health and fitness industry by surprise.
The internet was flooded with headlines like this one from the New York Times: “A Potential Downside of Intermittent Fasting — A rigorous three-month study found that people lost little weight, and much of that may have been from muscle.”
And this one from Insider “A doctor who has been intermittent fasting for years said he quit because his new study showed it has little benefit for health or weight loss.”
In case you haven’t seen or read any of the articles, the discussion was about the TREAT trial study that was recently published in JAMA Internal Medicine. The TREAT trial was a randomised controlled trial that looked at the efficacy and effectiveness of time-restricted feeding (TRF) on weight loss (the primary outcome) and metabolic health (the secondary outcome).
To determine the effect of 16:8-hour time-restricted eating on weight loss and metabolic risk markers.
In other words, the authors of the study wanted to see if TRF alone (without any further intervention like dietary restrictions, calorie restrictions, exercise or nutrition/habit coaching) would confer a significant weight loss and show improvements in metabolic health biomarkers.
(Note: Time-restricted feeding (TRF) is the term scientists use for any type of daily fasting regimens, i.e, 12:12, 31:11,14:10,16:8, 18:6 or 20:4 or OMAD). It’s us, the general public, that call the daily time-restricted feeding intermittent fasting).
116 overweight women and men were randomly assigned to either a consistent meal timing (CMT) group or a time-restricted feeding (TRF) group. The TRF group was instructed to eat all their daily meals between 12 pm to 8 pm (8-hour widow, 16:8 protocol). During the feeding window, they could eat whatever they wanted. No dietary restrictions. No calorie restrictions.
The CMT group was instructed to eat three structured meals per day, and they also received daily nutrition/healthy eating tips.
In the 12 weeks study, the average weight loss in the CMT group 0.68kg, and 0.94kg in the TRF group.
Time-restricted eating, in the absence of other interventions, is not more effective in weight loss than eating throughout the day.
Yes, you read that right. The average study participant in both groups lost less than 1kg in 12 weeks. I know you’re scratching your head right now, and thinking, “less than 1kg loss in 12 weeks? Seriously???” As I mentioned earlier, the primary objective of the study was to see if TRF alone (without any other intervention like dietary restrictions, calorie restrictions, exercise or nutrition/habit coaching) would confer a significant weight loss than a regular eating pattern.
Does Intermittent Fasting Work or Not?
What shocked many people wasn’t just the statistically insignificant weight loss between the two groups; it was the greater loss of muscle mass that was seen in the TRF group. Typically, when people lose weight, 20-25% of the weight loss can come from muscle mass. However, in this study, muscle mass accounts for a whopping 68% of the weight loss in the TRF group. That’s a perfect recipe for slow metabolism because of the role muscle mass play in total energy expenditure.
As someone who understands how time-restricted feeding works, I wasn’t surprised at the results. However, I was surprised at how some TRF/IF critics twisted the results of the study to suit their narratives. Anyone who can read beyond the abstract and media headlines knows precisely why the average participant in the study loss less than 1kg in 12 weeks.
And for the higher loss of muscle mass seen in the TRF group, we can make assumptions as to why that happened based on the data presented in the study.
For the insignificant improvements in metabolic health biomarkers, results from previous studies on TRF and chromo-nutrition have the answer.
Now, let me explain the reasons:
- the average person in that study lost less than 1kg in 12 weeks
- the TRF group lost more muscle mass
- there were no improvements seen in metabolic biomarkers.
Why The Average Person In That Study Lost Less Than 1kg in 12 Weeks
The TRF group ate ad libitum during their feeding window. What that means is they ate whatever they wanted, in whatever quantity they wanted during the 8-hour feeding window. Sometimes, we forget how easy it is to eat loads of calories within a short period.
Time-restricted feeding/intermittent fasting isn’t a magic bullet for weight loss. If your TRF/IF isn’t helping you to create daily calorie deficit, you’re not going to get any results. At best, you’ll lose less than 1kg kg in three months like the people in the study.
Therefore, if weight loss is the goal, how much you eat during the feeding window matters. IF/TRF won’t help if you’re stuffing yourself with too many calories during the feeding window.
Why The TRF Group Lost More Muscle Mass
When you lose weight, you’re making changes to each component of your body composition: water, fat, and muscles. In other words, when you lose weight, you lose a combination of water weight, fat tissues and muscle mass (lean tissues). Therefore, the loss of muscle mass seen in the study isn’t peculiar to TRF/IF alone. It happens with all weight loss protocols. As I pointed out earlier, between 20-25% of the weight loss typically comes from muscle mass.
Losing water and fat weight is cool. However, you want to minimise muscle loss so you can preserve your muscle mass. The reason is that the amount of muscle mass you have directly impact your basal metabolic rate. As I mentioned in my How To Fix A Slow Metabolism webinar, muscle cells are more metabolically demanding than fat cells. So it takes a lot of energy to maintain muscle mass. What that means is that when one loses muscle mass drastically, one’s metabolic rate will drop because of the drop in energy demand.
So the question is, why did the TRF group in the study lose more muscle mass than the control group? The data presented in the study gave the answers: the daily activity level of the participants in the TRF group went down.
“Data from the Oura ring reported about a 30% decrease (8555 to 6057) in steps from baseline to post-intervention in the group assigned to TRF compared to a 3% decrease (8871 to 8614) in the group assigned to CMT.”
We can extrapolate from this data that these folks weren’t working out. They weren’t doing the type of exercises that would help preserve muscle mass.
That’s why I pity those who are only obsessed with the number on the scale. That number doesn’t mean much unless you’re using a body composition scale that can analyse your body composition.
Yes, the scale is showing you’ve lost 10kg in 10 days, but what it isn’t showing it’s the type of weight you lost. Do you really think you lost 10kg of fat mass in 10 days? No ma’am! You lost mostly water weight as a result of glycogen depletion.
I also pity those who rely on dieting alone to lose weight. Dieting alone will result in a greater loss in muscle mass. What that means is that your metabolism will drop! To preserve muscle mass, you need to exercise. By exercise, I don’t mean walking and dancing alone. I mean incorporating resistance training into your fitness regimen
Resistance training does not only help preserve muscle mass, but it also helps increase the mass.
No Improvements In Metabolic Health Biomarkers
For many practitioners and proponent of TRF, myself included, we do TRF for its metabolic health benefits. So when this study reported no metabolic health benefits, I was like “hold on a minute! Why is the outcome of this study different from previous studies that have shown significant improvements in metabolic biomarkers?”
The answer was in plain sight: the timing of the feeding window and the distribution of energy within the feeding window (when the most calories are consumed) have the greatest effect on cardio-metabolic health.
The TRF group in this new study ate all their meals between 12 pm to 8 pm (late time-restricted feeding). In the studies that reported significant improvements in metabolic health, participants did early time-restricted feeding. In those studies, the eating window was 8 am – 2 pm, or 8 am -4 pm.
The late time-restricted feeding is the reason this new study saw no improvements in metabolic biomarkers. If like me, you practice TRF for its metabolic health benefits, please keep doing it. Studies have shown early TRF to be beneficial to cardio-metabolic health.
Would you like to know how to rightly use time-restricted feeding/intermittent fasting for weight loss, and improve health? Then you should join the November/December round of my 30-Day Intermittent Fasting Challenge.
Registration is now open. Click here to learn more about the programme.