When the fitness and weight loss world first found out about intermittent fasting (IF), it nearly collectively lost its mind. Many were told that you could fast for certain periods and then eat "whatever you wanted" within a certain feeding window, and still lose weight. Others realised this was a fallacy, and took to simply looking at it as another way to eat fewer calories than you burn. But when pop culture and media headlines take over it's difficult to sort fact from fiction. So, this article will get to the truth of whether or not intermittent fasting is better than standard dieting for fat loss, so you can decide if it's a good strategy for your fat loss goals.
What is Intermittent fasting: How long do I go without eating?
How long you go without eating totally depends on the approach you take. There are many ways to approach a intermittent fasting diet, but here are the three most popular:
- 16:8 (Fasting for 16 hours and eating for 8 hours).
- 5:2 diet (eating for 5 days and fasting for 2).
- Eat stop eat (E.g. Fasting on Tuesday and Friday -- a 24 hour fast once or twice a week).
Fasting simply is another way to eat fewer calories than you burn. In other words, staying in a calorie deficit.
There is simply no way to "hack" the body's system of weight loss and gain; eating whatever you want within an 8-10 hour window doesn't mean you'll negate any effects of body fat. It simply means there's potentially less chance you'll snack the day away between meals and finish up in a calorie surplus.
One study compared the differences in weight loss and changes in body composition between 1, 3, or 6 meals per day, and found no significant differences (1). The most important thing is to eat what suits you and your lifestyle the most.
Only recently was the most comprehensive analysis into intermittent fasting done, whereby 40 studies were reviewed, with 12 directly comparing intermittent fasting with a standard weight loss diet of eating regularly (2). They found "apparently equivalent outcomes” in regards to body fat loss and body composition change. They also found no differences relating to thyroid, cortisol, or sex hormones, though they concede more research is needed when it comes to those factors.
Perhaps most interesting to those of you lifting weights and wanting to lose fat, a study in 2015 compared an intermittent fasting approach to a normal dieting approach with the same weight training program, and again, no differences in fat loss were seen (3). The study's author spoke about how different people responded differently in both groups, declaring that intermittent fasting positively affected some people's food choices and others negatively. Some said the diet made them feel healthier and they ate better, whilst others then wanted to gorge on everything in sight when the feeding window came.
And so we return to our initial point, which is the most important thing anyone anywhere needs to know about weight loss:
There are no magic diets. None are better than others. Whatever approach you chose to ensure you eat in a calorie deficit, that best conforms to your personality and lifestyle, is the best choice.
More research examined intermittent fasting in 2020; recruiting 116 obese and overweight individuals for three months (4). The same outcome was observed: intermittent fasting did not help people lose weight significantly more than simply eating three meals a day.
Real-world examples: Fasting for fat loss
My best advice for people is to skip breakfast when weight loss is the goal. This is a happy medium between fasting and eating regularly.
For starters, Breakfast is NOT the most important meal of the day, and eating it makes no difference to how much fat we lose (1). Moreover, it does NOT "jump-start the metabolism" (1).
In fact, breakfast actually gives us the opportunity to eat more calories during the day; not ideal when you're trying to lose weight.
Note: If you absolutely must eat breakfast because you feel sick if you don't, and haven't really strived to become accustomed to going without it, then eat it.
Skipping breakfast isn't typically intermittent fasting in its most classic definition (as it's only really a 6 hour fast until lunchtime depending on what time you're awake). Furthermore, what I recommend you have for breakfast (black coffee and whey protein) is technically breaking the fast anyway.
But consider this example: Clint's macronutrient breakdown for fat loss is 180 grams of protein, 80 grams of fat, and 130 grams of carbohydrates.
Black coffee (a bit of milk is fine!) helps blunt appetite (5), whilst whey protein works wonders for keeping us exercising folk full and preventing overeating (6). So with Clint starting the day with this, he is preventing the trap of waking up to two pieces of toast, half an avocado, and a heap of salmon. That may well have been 25-30% of his allocated daily macronutrient allowance already.
So if Clint (and you!) can get into the habit of beginning to eat your daily macronutrient allowance by lunchtime, you're giving yourself a much easier and mentally achievable task for fat loss.
Many fall into the trap of thinking this "healthy" salmon and avocado breakfast will help us lose weight. But it won't if we get to dinner and we've already consumed our required calories for the day.
Anecdotally, most people report to me that the bulk of their food cravings come at night. So you want to be able to eat at night, and not get to 2 pm knowing you can't eat another thing!
As far as fat loss goes, intermittent fasting is not a magic bullet or a diet superior to any other.
It simply is another way to achieve a calorie deficit, which is the only precursor to weight loss there is.
If you find that waking up at 7 am and fasting until dinner is really easy for you to follow, then go for it! But if you find that's it's hell, consider a standard breakfast lunch and dinner, or the "skipping breakfast" alternative I presented.
Ultimately, it comes down to what you prefer, and what you can stick to. Because the only thing that guarantees weight loss is a calorie deficit -- a CONSISTENT calorie deficit!
(1) Young CM, Scanlan SS, Topping CM, Simko V, Lutwak L. Frequency of feeding, weight reduction, and bodycomposition. J Am Diet Assoc. 1971;59:466–472. 981-8.
(2) Seimon RV, Roekenes JA, Zibellini J, Zhu B, Gibson AA, Hills AP, Wood RE, King NA, Byrne NM, Sainsbury A. Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Mol Cell Endocrinol. 2015 Dec 15;418 Pt 2:153-72. doi: 10.1016/j.mce.2015.09.014. Epub 2015 Sep 16. PMID: 26384657.
(3) Tinsley GM, et al. Intermittent fasting combined with resistance training: effects on body composition, muscular performance, and dietary intake (poster presentation). J Int Soc Sports Nutr. 2015; 12(Suppl 1): P38.
(4) Lowe DA, Wu N, Rohdin-Bibby L, et al. Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med. 2020;180(11):1491–1499. doi:10.1001/jamainternmed.
(5) Schubert MM, Irwin C, Seay RF, Clarke HE, Allegro D, Desbrow B. Caffeine, coffee, and appetite control: a review. Int J Food Sci Nutr. 2017 Dec;68(8):901-912. doi: 10.1080/09637486.2017.1320537. Epub 2017 Apr 27. PMID: 28446037.
(6) MacKenzie-Shalders KL, Byrne NM, Slater GJ, King NA. The effect of a whey protein supplement dose on satiety and food intake in resistance training athletes. Appetite. 2015 Sep;92:178-84. doi: 10.1016/j.appet.2015.05.007. Epub 2015 May 12. PMID: 25979566.