By Doctor Philippe Guérin

“Ideas like footsteps are quickly erased”

 Walking – Saving the nomad within us. By Pascal Picq – Otherwise Ed.

Intensive sport makes you lose weight: belief or reality?

In the realm of obesity, a stubborn myth freezes specialised discourse. It is the source of much wasted effort, wasted suffering and despair. This is the universally held belief that participating in sports leads to weight loss, that the more intensive the effort, the more significant the weight loss.

There is no doubt that increasing effort compared to resting causes us to burn more energy, a value commonly measured by an amount of “calory expenditure”. So after an intense exercise session we would have “lost” for example, around 500 calories and maybe a kilogram in 2 hours.

In fact, weight gain or loss shares a complex physiology which is dependent on many factors: energy and food of course, but above all, hormones influenced by stress, acute or chronic inflammatory processes, the composition of our microbiota and the variation in blood pressure, quality and quantity of sleep, among others.

In a transient sporting context, the small kilo lost is only an ephemeral event. By re-eating, even a little, the “spent” calories are quickly replaced and the water evaporated through perspiration, mainly responsible for the kilo lost, is quickly compensated for. The sporting episode only “spent” an immediately available and immediately rebalanced “calorie” reserve. The bulk of fat reserves, effective protection against days of famine, cannot be influenced by a temporary effort.

The desire of obese patients is to (re) become thin, long term. There is no study to show that intensive sport helps you lose weight in a sustainable way. It is the problem of the overweight person who constantly hears from relatives, institutions, doctors and other wise counsellors the nagging, forbidding and guilty warning “that it is necessary to exercise vigorously” to lose weight.

The important question to ask is: how to reduce these famous reserves (of fat) and thus lose weight sustainably? There is not much that physical activity can do on its own, but it is essential.

 More athletic and more sedentary: what a paradox!

We are discovering that more and more French people are obese (around 7 million people in 2021).

However, we have never done so much sport. Paradoxically, from the second half of the 20th century and increasingly since the 21st, our time for physical activity has continued to decrease.

This is the great paradox of our time! The practice of sport has become popular, but the time spent moving has dramatically decreased. We are the champions of indoor sports activities in the evening, of the number of kilometres of “jogging” on Sunday morning, but in fact every year we smash the record for the time spent sitting. Work, seated transportations and digital leisure have transformed the conqueror and explorer biped that we are into a motionless creature. We have discovered the effects of a sedentary lifestyle, harmful and unheard of until now, to our great misfortune.

What happens when we sit down?

The electrical and muscle activity in our legs stop, reducing our energy consumption by about 1 calorie per minute of rest. Sitting for too long increases our physical deconditioning, which compromises muscle performance and involves a possible period of reconditioning, which we call re-training if we want to “get back in shape.” Enzymes that help break down fat molecules (lipolysis) are produced in lesser quantities or disappear for lack of usefulness, thus facilitating storage processes.

After two hours of sitting, our HDL cholesterol, what many doctors call “good cholesterol”, drops by 20%. After 24 hours, the effectiveness of insulin decreases and must therefore be secreted in abundance for the same effect, thus aggravating the risk of resistance to this hormone and beyond that, to  diabetes.

All of these risk factors are well documented in the literature as they are the root cause of several diseases, leading to a high economic burden for society in addition to being a serious public health problem.

A 2021 study published in Lancet Planet Health shows that adopting moderate daily walking habits would reduce the number of deaths due to physical inactivity by about 1.15 million by 2040 (study done in 9 countries including China, United Kingdom, United States, Germany, Brazil, India, Nigeria, Indonesia and South Africa).

The COVID-19 crisis has increased our knowledge at the expense of the chronically overweight sedentary “inflamed” and could worsen these numbers.

The list of harmful effects is long (see table above) ...
The list of harmful effects is long (see table above) …

What does regular walking bring?

Moderate exercise, either walking for 30 minutes a day or simply 5,000 steps a day (not forgetting to get up every hour if our work requires us to remain seated) have unsuspected benefits. The goal here is not to perform well or to burn as many calories as possible but to maintain a body programmed for walking which imperceptibly, atrophies in the event of chronic immobility (see table).

These daily exercises are enough to regulate our hormonal responses to stress, benefit our immune system, increase our anti-inflammatory capacity, increase insulin sensitivity, and improve our mood and cognitive abilities.

Daily walking is a vector for improving the quality of sleep by favouring the stages of slow sleep, a period favouring the secretion of growth hormones which facilitate the body’s repair functions.

Walking is the initial, so-called first-line treatment for all depression. It has been shown to be beneficial more often than the effect of antidepressant drugs.

Fast walking or slow walking ?

We are talking about walking at a moderate pace without exceeding what is called the anaerobic threshold, which generally corresponds to the dyspnoea threshold (the moment when we feel short of breath when we walk and which forces us to slow down).

• By exceeding this threshold we attack our body which defends itself by producing inflammatory cytokines insufficiently compensated by those with anti-inflammatory properties.

• By walking too slowly or too little, during a fast, we risk to not sufficiently stimulate the growth of our muscles and thus to not generate a phenomenon of functional protein shaping, at this level. This goes against “hygienists” theories which suggest the practice of fasting at rest.

Fasting: an obstacle to walking?

Most of the structures that offer fasting support organize physical activities, the most common of which is walking. Not eating and walking, however, seem to be opposing occupations. In fact, by fasting we do not eat but we feed ourselves. We are consuming our reserves; sugar circulating at the start then sugar from the glycogen in the liver in the first day, then fat as much as our reserves allow us. There is no starvation in fasting.

On the contrary ! Imagine our Cro-Magnon ancestors in the middle of winter without food reserves, dazed and immobilized by the lack of energy due to an unobtainable food. Eat or die. The scenario is possible but does not seem serious. Our species survived because of the potential for travel efforts even on an empty stomach. The only way to fill it in the absence of crops is to walk with the goal of finding food. For this, our ancestors had to keep their full physical capacities and above all develop their intellectual faculties so as not to take the wrong route, plan a hunt, remember the best places as well as possible while protecting the weakest of the tribe. Fasting and walking actually increased the physical and intellectual faculties of humans at the time.

Our bodies have not changed. They just have (a little) lost the habit of missing. We believe we weaken ourselves by skipping a meal, but in fact, passing this now unusual and uncomfortable milestone, we can experience a surprising sensation of physical “top shape” and a certain progressive clairvoyance. It is still necessary to try the fasting experience and understand a minimum about human physiology to be reassured.

Fasting is therefore not an obstacle to walking, on the contrary. Our body provides sufficient energy to walk, for a long time, and at different speeds depending on the danger or the goal to be achieved.

What is the common element of fasting, walking and sleeping?

We now know that not eating is not “not eating” and therefore physical exercise can be safely continued. But why does this situation also improve our “clairvoyance”? In 21st century language we would speak of cognitive optimization and neuronal plasticity …

This is exactly it; fasting allows us to improve our mental and cognitive abilities.

If we take the example of our non-fed Cro-Magnon ancestors, how can we explain that they could (had to) think better and faster to find solutions. Their survival depended on it. We already know that the breakdown products of our fat stores, ketones, are soothing to our neurons which, together with the intake of sufficient sugar provided by gluconeogenesis, does not lack energy to function.

In stressful situations, it is not enough to optimize the action of existing neurons. You have to exercise your memory, assess the dangers, conjure up strategies, listen to your senses and other members of the tribe and finally come up with potential solutions. It must be understood that these circumstantial actions were only possible thanks to the creation of new synaptic connections and the creation of new neurons (neurogenesis).

This adaptive phenomenon is dependent on Neurotrophins,for which the leader is BDNF (Brain Derived Neuronal Factor). You’ve never heard of it. This is normal because the discovery of the multiple functions of BDNF and other neurotrophins is recent. They allow us to forget the assertion of a great Nobel Prize winner at the beginning of the 20th century (Pablo Y. Cajal) who considered that from the age of 20 we lose many neurons daily, which explained our inevitable state of dementia in end of life. It may seem logical, but how then can we explain the freshness of spirit of Edgar Morin, Stéphane Hessel, Jean d´Ormessons and others at a very advanced age?

The BDNF is probably the main explanatory element.

And do you know what promotes the production of BDNF?

Fasting, daily walking and good sleep!

With Fasting & Health we accompany you during your fast (but with us no stress), we walk daily to an appropriate rhythm whilst awakening our senses and we work together to improve the quality and quantity of sleep.

Thanks to these three goals of care, we optimize the therapeutic and preventive virtues of the different types of fasting.

Doctor Philippe Guérin

Doctor Philippe Guérin supervises fasting retreats in France, in our Fasting & Health institute in compliance with current health regulations (PCR test requested).

  • a comprehensive medicalized and personalized approach.
  • sustainable weight loss 
  • a stress free groundwork preparation in order to implement long-term habit-based dietary behaviour changes.


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