Yes, intermittent fasting (IM) can be a powerful weight loss tool without the need for exercise. In fact, you do not need to take part in too much physical activity at all to lose weight. The only thing you truly need to do to lose weight is maintain a caloric deficit.
Of course, it’s easier to maintain a caloric deficit at higher activity levels. However, exercise is not necessary for weight loss – the only thing that really matters is the caloric deficit.
Use a BMR calculator to work out how many calories you need for your biometrics and activity levels, cut 500 from the total, eat this amount, and you should lose roughly 1lb/0.5kg per week. This is regardless of your activity levels.
In addition to maintaining a caloric deficit, there are some dietary hacks you can put in place to make your weight loss journey far more efficient. Of these, IM is amongst the best.
The pattern of eating required under an IM protocol underpins its success in every way – it allows the body time to fast, which will have really quite profound results on the body. This fast will rest the digestive system for extended periods of time, whilst simultaneously leading to hormonal and metabolic changes that are beneficial to body fat loss.
Unlike most ‘diets’, IM won’t restrict what somebody eats. The most important factor is following a very careful plan that manipulates when somebody eats.
You can eat large meals on an intermittent fast. In some IM protocol variants, they are required – if you are only eating one meal per day, or trying to get everything in over four hours, you will need to be prepared to eat a lot at once.
Nevertheless, these large meals will still likely be part of an overall caloric deficit, as they will be accompanied by long periods of fast. These deficits will usually be relatively effortless, or at least you will not need to specifically try to maintain them. This is the first potent weight loss tool in the IM toolbox.
You will struggle to not maintain a caloric deficit following an IM protocol, regardless of your activity levels.
Aside from this deficit, most of the truly beneficial weight loss aspects come from the biology underpinning the fasted state itself, and have very little, if anything, to do with activity levels.
The Fasted State
The fed state lasts from the beginning of a meal to about 3-5 hours after it is finished and will be the period in which the body is digesting food, breaking it down and absorbing nutrients.
Energy will go into this digestion- it has a thermogenic effect. However, in the vast majority of cases, more energy will be brought into the body than is used in digestion.
Insulin levels will spike as this energy is brought it, and glycogen levels and blood sugar levels will be raised.
This fed state is followed by the post-absorptive state. This can last until up to 12 hours after the body’s last intake of nutrients and calories. The body will not be digesting food during the post-absorptive state, and insulin levels shouldn’t be too high, but glycogen levels will be raised.
After this comes the fasted state, which is, of course, the cornerstone of any intermittent fasting protocol. This happens 12 hours after the last nutrient intake (so can only occur when nothing has been eaten for 12 hours.) At this point, a few things occur at the hormonal and cellular levels.
During the fasted state, insulin levels fall to their lowest and body fat becomes more accessible as an energy source. This means that physical activity will be more efficient for weight loss during the fasted state, as it will be burning through fat.
However, even at rest, the body’s metabolic demands will see you using up body fat as fuel, showing that IM will work well enough without exercise.
Alongside insulin and fat release benefits, cells also begin repair processes during the fasted state. These are generally halted or impaired by the digestive process.
Genes like human growth hormone (HGH) aren’t expressed in large enough quantities when the body is digesting nutrients. During a fast, they are. This, again, will make exercise more efficient, as muscles will respond to stimuli and repair faster.
However, exercise still isn’t necessary, particular for weight loss – the benefits are there to be gained either way.
Fasting can also increase adrenaline and noradrenaline hormonal output, both of which enable your body to utilise more body fat- especially visceral fat- for energy.
These effects have been found to come into play even at rest, meaning that those going through frequent fasting periods will be burning more body fat just sitting around.
A Roundup of Benefits
So, to recap, the following benefits can be gained from regularly including extended fasting periods in your diet:
Insulin sensitivity improves, and all levels of insulin drop. This can aid in reversing the effects of related diseases like diabetes, alongside making body fat stores more accessible.
HGH levels increase, which can be quite drastic, with levels increasing by as much as a multiple of five. HGH is crucial for weight loss and hypertrophy, so will be of benefit to those looking for body recomposition.
Cells repair in the absence of the digestive process, including the digestion and removal of dysfunctional, old proteins that build up within cells.
Gene expression, with changes in the function of genes related to healthy weight maintenance, protection from disease and the maintenance of longevity being the most affected.
IM and Weight Loss
The above benefits will account for much of the weight loss associated with intermittent fasting.
The body’s ability to process visceral fat as a form of energy, rather than simply using blood sugar and glycogen reserves, will mean that fat stores are used up. They will deplete.
In addition, the increase in HGH production will help to promote healthy muscles mass (especially, though not uniquely) in those undertaking a rigorous exercise schedule.
Muscle mass is very metabolically demanding, meaning that increased amounts will lead to increased energy demands, thus helping to create a caloric deficit.
The importance of IM’s effects on insulin levels cannot be overstated. High insulin levels, and the associated excess insulin in the blood stream, will lead to more frequent, more intense hunger pangs, as well as rapid dips and spikes in energy levels. Decreased levels, conversely, will help to control hunger and energy levels, especially during longer fasts.
Essentially, you will feel less hungry and won’t experience energy crashes when following an IM protocol. You will crave food far less, making it far easier (and far more comfortable) to maintain a caloric deficit, no matter your caloric, metabolic needs.
There is also evidence to suggest that IM will increase your metabolic rate in its own right, divorced, or at least largely separate, from possible improvements to hypertrophy. Rodent studies have found that intermittent fasting reprogrammed metabolic pathways in order to maximise energy gained from food.
Though many of the sought-after benefits of intermittent fasting come from the above biological changes inherent to the fasted state, one of the key aspects of weight loss is caloric load.
As we have already seen, if the human body takes in less energy (fewer calories) than it needs, it will burn body fat and lose weight. This is a near enough universal rule. Though this can be achieved without running an IM protocol, simply by following any number of cutting diets designed to limit caloric intake, it is more easily done during intermittent fasting.
These factors are all improved by incorporating regular exercise into your lifestyle. You will likely be healthier for doing so. However, none of these factors rely on exercise – the benefits can be gained even when IM is run in tandem with a sedentary lifestyle.