Fasting is very in at the moment. Despite being popularised thousands of years ago by various religious sects and being present in almost every single society and religious practice since the dawn of time it is undergoing a very modern rebirth.
Skipping meals was once fitness heresy. All through the 90s, it was a widely held belief that if you wanted to get into shape then you had to eat 6 meals a day, at regular intervals, to keep the metabolism purring like a well-groomed feline. If you went without protein for longer than 3 hours then unspeakable things would happen to your body as you enter the inner circle of catabolism and experience soul destroying loss of gains. If you were skipping meals regularly then you might as well not bother training at all.
As you can imagine this mindset created a high barrier to entry for every day, non-gym obsessed person.
Ori Hofmekler published his Warrior Diet which utterly rejected the notion that the Bodybuilder approach was the correct approach to physical mastery. He built a pseudo-historical thesis on the idea that the great warriors of yore, the Roman centurions, in particular, subsisted on meager rations through the day and a hearty feast in the evening. He proposed a 4-hour feeding window.
Martin Berkhan, the godfather of intermittent fasting pioneered a 16/8 'Leangains' approach to dieting. The controversial Swede maintained year-round extreme leanness whilst possessing excellent muscular development and strength levels. More than anyone he challenged the status quo of multiple meal feedings being superior to restricted feeding windows. Crucially he did this by referencing scientific papers rather than referencing historical anecdote.
Brad Pilon, operating at roughly the same time as Berkhan released his book Eat, Stop, Eat. A Fasting manifesto which explored a lot of the data around fasting.
More recent incarnations of these approaches are the 5/2 diet- eat normally for 5 days and severely restrict your food for 2. Gregory O'Gallagher has essentially repackaged the 16/8 approach with his own spin to great effect and Berkhan has come out of the wilderness after a long hiatus.
So far so fitness. Why the sudden interest in fasting? Mainstream science has been giving fasting some attention of late which has lent a decent amount of credibility to the practice. Valter Longo, in particular, has been examining the impact of restricted feeding windows in rodents. Most of the benefits associated with fasting seem to be centered around the process of autophagy. This cellular clean-up process is triggered by a fasting state and helps to optimize cellular repair and mitochondrial function.
The idea is that there are discrete benefits to fasting above and beyond the calorie restriction aspect.
Episodic periods of scarcity are more beneficial for the body than chronically low-calorie diets.
Why is time restricted feeding controversial?
Reducing the amount of time we are spending in a fed state shouldn't be particularly controversial. The hyper fed state we are encouraged to exist benefits the food industry more than the individual. Snacks aren't normal. Healthy snacks aren't normal.
A snacking culture erodes the significance of mealtimes, once they're deemphasized nutritionally they fall by the wayside socially and we become an increasingly fractured and alienated society. The populations that live longest are the ones that retain the social element of meal times.
So what are the benefits of fasting? And how do they apply to you?
If you're interested in weight loss then intermittent fasting might be for you. You might be able to limit your eating window and not focus on calories or macros and still lose weight. This will still be due to accidentally arriving in a calorie deficit.
If you already skip breakfast and want to adopt a sciencey sounding validation for something that you're going to do anyway then Intermittent fasting is definitely for you.
If you prefer to eat fewer larger meals then go right ahead, this might be for you.
However, thus far there is no proven advantage to intermittent fasting versus the good old fashioned calorie deficit and eating well.
Can intermittent fasting exacerbate an existing issue with food? Can it legitimize disordered eating patterns? Sure, it most certainly can.
Can it be liberating for someone who has developed an orthorexic attachment to multiple meals, who brings tupperware into work meetings and restaurants? Of course.
Context is everything. Where you've come from when you encounter something like fasting will dictate whether it is a poison or a cure for you.
Most people need more structure with their diets, not less. We live in an obesogenic environment that is incredibly hard to navigate successfully and the majority of people will benefit from an approach that prioritizes a basic understanding of macronutrients and food quality. There is a danger that intermittent fasting can reinforce and legitimize a starve/binge pattern, so there is a certain subset of clients I would steer well clear of fasting as a practice.
If you're a well-muscled athlete who trains hard multiple times per week then you might struggle to fit in enough food in a shortened eating window. Just as it might accidentally place someone in a calorie deficit so it might make it very difficult for a hard training athlete to consume sufficient calories to fuel their training.
The major advantage of fasting is not having to worry about food. It's liberating. You can be more productive as you're not panicking about eating. Whilst most people benefit from more structure initially, for many people this can become a source of stress.
You can get the same benefit from outsourcing your food prep to the experts.
Consider shortening your eating window- don't jump in at 16/8, there will be a considerable benefit to practicing a 12/12 split or 14/10 split. For many people setting some arbitrary time restrictions works well as a way of regulating and limiting calorie intake.
Match activity levels with intake- fuel your training. Add more food in around training and less on non-training days.
Understand that meal frequency really comes down to preference and practicality. Do you like eating 6 meals a day? If you'd rather eat 3 larger meals then please do that.
Is it practical to consume 200 grams of protein in 2 meals per day? Maybe not, in which case you'll probably benefit from more feedings.