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Intermittent Fasting - Magic Formula or Just Another Tool?
Don't just believe what you read on the internet (like right now), instead look for the evidence which you can find here... at Strength Framework.
Mark Christie
October 14, 2024 • Estimated Reading Time: 12 minutes
Like so many other diets, they come in and out of fashion. Keto, Carnivore, Fasting, Atkins… You will have people you know, who follow one for a period and tout their amazing magical fat loss benefits.
In this article I want to look at all the scientific evidence around intermittent fasting, not just what your aunties best friend said worked wonders for them.
Benefits claimed include: Longevity, fat loss, heart health, protection against type 2 diabetes.
Funnily enough, just losing body fat, being at a healthy level of body fat and being active, has all the same benefits. Who would have thought….
IN THIS ARTICLE:
GETTING STARTED
What is Intermittent Fasting
Intermittent Fasting, often called Time restricted eating is a timed eating pattern at which you fast for so many hours of the day and eat during your “eating window”.
There are two main protocols people follow when implementing intermittent fasting:
The 16:8 Method - This is where your eating window is only 8 hours per day and for the remaining 16 hours you fast. So if you started eating at 8 am, you would finish eating at 4 pm, fast for the rest of the day, and start eating again at 8 am the next day.
The 5:2 Method - This protocol has you eat as normal 5 days per week, ie Monday to Friday. On the other 2 days, you fast and consume one 500-600 calorie meal per day.
On top of the above two methods, you have two other relatively popular protocols which people turn to, to help their weight loss goals:
The Warrior Diet - Which is a more extreme time restriction with a 20-hour fast and a 4-hour eating window.
Eat Stop Eat - Which incorporates one full 24-hour break from eating at least one day per week. But then, for the rest of the week, you eat according to your desired schedule.
Basically, like all “diets” intermittent fasting is a restriction diet. It’s just unlike the keto diet for example, which restricts carbs, intermittent fasting restricts your eating window.
DROP THE SCALE
Intermittent Fasting Results On Weight & Body Fat Reduction
The main reason most people turn to fasting is for weight or body fat loss, so I want to look at the evidence behind that first.
A large meta-analysis by (Gu et al., 2022) which included 43 randomised controlled trials with 2,483 participants and interventions lasting at least 1 month and an average length of 3 months.
They aimed to compare results against IF (Intermittent Fasting) vs a NID (non-intervention diet), with no calorie restriction for IF vs CR (calorie restriction).
The meta-analysis included results from trials which included all of the above methods of fasting, (5:2, 16:8, The warrior diet and eat stop eat).
Firstly, for those of you who lift, some of the studies included in this meta-analysis included IF vs CR while performing physical exercise (some included cardio, lifting and some included both). The results showed that IF was “about as” effective as CR when included with a physical exercise routine. The IF did however have a slight benefit over CR when it came to WC (Waist Circumference) reduction.
Intermittent Fasting vs Non-Intervention Diet.
The review also looked at blood glucose levels, insulin concentrations and HOMA-IR. Finding that blood glucose concentrations didn’t differ between IF or NID. Insulin concentrations and HOMA-IR were found to be slightly more in favour of IF.
It was found that between IF vs NID, IF was more beneficial in reducing body weight, WC, and FM (Fat Mass) without affecting lean mass.
Intermittent Fasting vs Calorie Restriction.
👉 The main reason most of you are here, reduce calorie intake without IF or reduce calorie intake with IF implemented…
IF results did not add any benefit over standard CR other than slightly better WC reduction.
Thus, while IF was discovered to be superior to the non-intervention diet in this study, it was unclear whether time restriction or energy restriction played a greater role.
Although IF did not restrict calories in some of the included studies, it is suspected in this study that CR may be dominant as time restriction did not seem to play a role.
A relatively new randomized controlled trial by (Maruthur et al., 2024) on 41 obese adults with an average age of 59, looked at the effects on weight loss and fasting glucose when following a time restricted eating (TRE) window vs usual eating pattern (UEP) when calories were matched. The Results showed that time restriction eating pattern did not improve weight loss more than a non time restriction diet.
In the setting of isocaloric eating, TRE did not decrease weight or improve glucose homeostasis relative to a UEP, suggesting that any effects of TRE on weight in prior studies may be due to reductions in caloric intake.
A 3 month study by (Keenan et al., 2022) which included 34 untrained subjects, were split into two groups. Group 1 followed a standard daily 20% calorie deficit, while the other group followed the 5:2 intermittent fasting protocol with a 70% deficit on those two days and euenergenic consumption on the other 5. With both groups prescribed to consume 1.4g per kg of bw/per day of protein.
These subjects also undertook 2x resistance training sessions per week and 1x resistance and aerobic combined session per week unsupervised.
Due to the stimulus of training and adequate protein intake, LBM (lean body mass) increased significantly in both groups, while body weight and fat decreased with no difference between the groups.
Both groups increased thigh muscle size and reduced intramuscular and subcutaneous fat assessed by ultrasonography and (pQCT) peripheral quantitative computed tomography. With both groups resulting in similar strength and muscle endurance outcomes.
One notable difference: the daily calorie restriction group displayed increased overall muscle surface area than the intermittent fasting group.
GROWTH
Intermittent Fasting For Lifters (More Information)
A study by (Stratton et al., 2020) took 26 recreationally trained males on a 4 week intervention to compare IF vs non time restricted feeding, while calorie intake was matched with a 25% calorie deficit in each participant to promote fat loss, while maintaining 1.8g per kg / per day protein intake.
The participants followed 3 full body training sessions each week, as shown below.
Note: I like how the authors of the study have included their training intensity using the RIR scale (which we have covered before) and rest times.
Figure A: From (Stratton et al., 2020)
Both groups experienced similar significant decreases in body mass, fat mass, body fat percentage and testosterone, while increasing biceps and vastus lateralis muscle size.
Both groups also experienced similar increases in their bench press 1RM, leg press 1RM, and vertical jump height.
Figure B: From (Stratton et al., 2020)
In conclusion, intermittent fasting does not enhance the results you achieve over calorie restriction alone. However can be used as a viable strategy to meet your goals if it suits your lifestyle without harming results.
A clinical trial which included 34 resistance trained males, by (Moro et al., 2016) looked at the effects of utilizing the 16:8 time restriction window vs a normal eating pattern, with both groups at maintenance calories for 2 months.
The intermittent fasting group had 3 meals at 1pm / 4pm & 8pm.
The normal eating pattern group had 3 meals at 8am / 1pm & 8pm.
Both groups were matched for calorie intake and macronutrient distribution.
After the 8 weeks, the fasting group saw slightly more fat mass decrease. While fat free mass, muscle size and maximal strength was the same in both groups. Testosterone and insulin-like growth factor 1 decreased significantly in the intermittent fasting group, with no changes in normal diet.
No significant changes were detected in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides.
TLDR
Key Takeaways & Practical Applications
When calories are not matched, intermittent fasting can work well to help reduce calories and improve health markers by reducing the time available to eat. Leading most to consume less calories.
When calories are matched, intermittent fasting has no benefit over standard calorie restriction.
For lifters, intermittent fasting or following a time restricted eating window does not seem to have any negative effect on muscle size and performance outcomes and results in the same end result as calorie restriction.
If intermittent fasting, or following a time restricted eating schedule helps you adhere to your desired calorie restriction the evidence shows it can be a viable method to do so.
At the end of the day, intermittent fasting is just another tool to help you eat less calories.
Think about it, you will effectively remove one or two meals depending on the eating window you choose to follow. It will become harder for you to eat enough calories in a shorter time frame unless you live at mcdonalds, in which case you will have a hard time putting yourself in a calorie deficit.
If intermittent fasting suits your lifestyle, works around your schedule and is easy for you to adhere to, then that’s a great dieting tool to use.
Adherence is priority number 1 when it comes to training and nutrition afterall.
Till next time,
Keep Training & Keep Pushing.
Mark ✌️