Exercise and muscle fat

Regular readers of this blog are now familiar with the health risks associated with visceral obesity, defined as an excess of fat located in the intra-abdominal cavity. Although this form of obesity is very dangerous to health (cardiovascular disease, type 2 diabetes, cognitive decline and dementia, sleep apnea and some forms of cancer), the good news is that it can be mobilized by recalibrating diet and regular physical activity and exercise.

Indeed, we have carried out several lifestyle studies in our laboratory in which we have shown that for a weight loss of about 5 to 10%, participants could lose 25% of their visceral fat and sometimes more. In addition, this decrease was associated with substantial improvements in their health profile.

Fat in the tissues

In addition, other body composition indicators are modified in individuals with visceral obesity. Indeed, imaging work (axial tomography and magnetic resonance imaging) from many laboratories around the world, including ours, has shown that visceral obesity is often accompanied by an accumulation of fat in normally lean tissues such as the heart (epicardial and pericardial fat), liver and skeletal muscles. This accumulation of fat is called ectopic fat.

Since visceral obesity is the result of a refined, sugar-rich and calorie-dense diet with a sedentary lifestyle, the muscles of individuals affected by it are often atrophied (loss of muscle mass). That is why in the exercise physiology laboratory of the PEPS at Université Laval, where I began my university studies in the 1970s, we were interested in measuring the percentage of body fat and muscle mass.

Although it has long been known that regular physical activity can reduce the percentage of body fat and maintain or even increase (depending on the form of exercise) muscle mass, recent imaging work has shown that it is necessary to go beyond simply measuring muscle mass to properly evaluate the effects of exercise training.

Indeed, patients with visceral obesity not only very often have decreased muscle mass, but these muscles are infiltrated with fat. What are the health consequences of this fat infiltration into the muscle? This is still a matter of debate, as researchers are still unsure of the contributions of these different fat deposits in muscles to the complications of visceral obesity.

In one of our recent research projects, we measured by axial tomography the amount of fat found between the various muscle groups of the thigh (red in the right images) of our visceral obese participants (red in the left images), as well as that inside the muscles (yellow in the right images). We then trained these male volunteers with visceral obesity by prescribing 160 minutes of moderate intensity exercise per week.

The results of this study, based on the work of one of our master's students, Alexandre Maltais, have just been published in the journal Medicine & Science in Sports & Exercise. Before the intervention, and as reported in several studies, we observed that visceral obesity was indeed accompanied by an increase in lipids in the muscles of our participants.

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Indeed, we notice in the image at the top right that the muscles were marbled with fat (in yellow) and were of lower density, reflecting fat infiltration (a fat muscle is of lower density than a lean muscle). As a result of the procedure, the subjects not only improved their fitness, health profile and lost visceral fat (lower left image), but also lost some of this fat infiltrating their muscles and their muscle density increased (lower right image).

This study therefore confirms that exercise training not only reduces visceral fat that is dangerous to health, but also melts the fat between the various muscle groups, as well as the fat that infiltrates the muscle.

Thus, if you move from sedentary to physically active lifestyles, not only will you lose visceral fat and notice a decrease in your waist circumference, but exercise will induce imperceptible changes in the composition of your muscles, which, at comparable volume, will be thinner than those of a sedentary individual.

To simplify things, we often talk about maintaining our muscle mass through exercise (a clear advantage of exercise over a restrictive diet), but keep in mind that at comparable volume, a lean muscle in an individual who is active regularly is much more compatible with health than a muscle that is completely infiltrated with fat in a sedentary individual.

Which fat is good for you?

Fat is not the enemy of our health! The key is to consume the right one.... The point with Michel Pereira, naturopath.

Fat or fats are called lipids. Together with carbohydrates and proteins, they cover our daily energy needs. Lipids are important to build our energy reserve, the envelope of our cells, our steroid hormones (estrogens, testosterone, cortisone...), our brain chemical mediators and our chemical messengers of inflammation. When they are digested by the intestine, thanks in particular to bile salts and our pancreatic enzyme, they are broken down into fatty acids. These fatty acids are of different types: saturated fatty acids and unsaturated fatty acids

Saturated fatty acids

They are found in foods of animal origin, such as butter, whole dairy products, some meats. It is also found in vegetable fats, especially tropical oils (palm, coconut). They should make up about a third of our fat intake.

Being saturated, they are difficult to metabolize by the body and tend to store in fat cells. If consumed in excess, they can make the membranes of our cells too rigid, which prevents, for example, red blood cells from slipping into small blood vessels (risk of clotting) or does not allow nerve cells to receive important chemical messages (risk of depression). However, they are still important for our body because they are an important source of vitamin A.

Unsaturated fatty acids

An unsaturated fatty acid is more unstable and therefore more sensitive to oxidation (they will turn rancid). On the other hand, the more unsaturated (polyunsaturated) it is, the more mechanically flexible and flexible it will be. Hence the interest of these fatty acids in the flexibility of cell membranes. Unsaturated fatty acids include monounsaturated and polyunsaturated fatty acids.

Monounsaturated fatty acids

Contained mainly in olive oil, rapeseed oil but also in avocado, hazelnut, macadamia and pecan nuts, they are also known as omega 9. Monounsaturated or omega 9 fatty acids are good for cardiovascular health. They should make up about half of our fat intake.

Polyunsaturated fatty acids (PUFAs)

They should make up about one-sixth of our fat intake.

There are 2 families: Omega 3 (ω3) and Omega 6 (ω6).

The Omega 3s

In the omega 3 family, the leader is alpha-linolenic acid, which is transformed by the body into EPA and then DHA. The main sources of alpha-linolenic acid are perilla, flax, camelina, rapeseed and walnut oils. Sources of EPA and DHA are cold sea fish (mackerel, sardines, salmon, herring, tuna) and capelin and cod liver oils.

The health benefits of ω3 are extremely broad. They will be particularly recommended for pregnant and breastfeeding women, the elderly, in the protection against cardiovascular, neuropsychic, inflammatory, hormonal, dermatological disorders...

The proper use of omega 3 by the body can be hindered by:
  •  Age (>70 years)
  •  Excess saturated, trans fatty acids, sugars
  •  Stress, smoking, alcohol
  •  Excess omega 6

The Omega 6s

In the omega 6 family, the first of the line is linoleic acid, which is also transformed by the body into gamma-linolenic acid and then into arachidonic acid. Linoleic acid is derived from plants and in particular from safflower oils, grape seeds, sunflower, corn, walnuts, soya, wheat germ, squash, sesame....

Gamma-linolenic acid is present in evening primrose, borage and blackcurrant seeds. The health benefits of omega 6 in this form include the regulation of hormonal disorders (female cycle, premenstrual syndrome...) and skin problems.

Arachidonic acid is of animal origin: meat, offal, eggs and linoleic acid is processed by the body if there is a too low intake of omega 3 and/or an excessive consumption of sugars and trans fatty acids.

Excess arachidonic acid causes inflammatory and autoimmune diseases, cardiovascular diseases and metabolic disorders (obesity and diabetes).

These fatty acids are very fragile, they oxidize quickly on contact with air and heat. Vegetable oils must be stored in a cool, dark place, not heated and must be first cold pressed.

Linoleic acid (ω6) and α-linolenic acid (ω3) are called "essential" because they cannot be synthesized by the body. They must be provided by the power supply.

Ensure the Omega 6/ Omega 3 ratio

In modern food, there is a preponderance of saturated fatty acids and a ratio ω6/ω3 that is far too high, due to the high consumption of sunflower oil rich in ω6. The objective with polyunsaturated fatty acids will be to find a good balance between them, i.e. to find an optimal omega-6/omega-3 ratio close to 2 to 3. If you have too much omega-6 in your diet, inflammatory phenomena will be stimulated and the blood will be less fluid, which can lead to heart attacks or certain cancers, for example. If you have too much omega-3, the risk of heart attack will be very low because the blood will circulate perfectly well and even too well: so the risk of a hemorrhagic stroke will be higher. Currently, for a large part of the European population, the ratio ω6/ω3 is around 10 to 15 to 1 and even more.
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Trans fatty acids, to be avoided at all costs!

An unsaturated fatty acid molecule has a configuration called "cis". When the configuration of this molecule is altered by heat or transformation processes, it is called "trans" and loses the properties of polyunsaturated fatty acids. Their consumption increases cardiovascular risks in particular. They are present in some industrial oils and margarines but also in a less visible way in chips, crackers, etc... (in the form of hydrogenated oils).

Fat, a hard drug for the brain?

In obese people, high-fat foods would act like hard drugs in addicts. This is what a CNRS team discovered... in mice. And for good reason, triglycerides would also act on the reward circuit. Explanations.

The brain only feeds on glucose. The body uses fats and other sugars as energy sources. However, an enzyme capable of identifying and breaking down triglycerides, fats from food, is present in the brain area called the "reward center". "It could be there to tell the brain how much triglycerides there are in the body," explains Serge Luquet of the Functional and Adaptive Biology Laboratory (CNRS/Université Paris Diderot).

The satisfaction of a good meal

What happens when the mouse consumes fat? To find out, this researcher and his team have silenced the gene encoding the triglyceride detection enzyme. The result: the animals then show a desire to eat fat, and a tenfold motivation to find this reward.

Then, the researchers simulated the action of a rich meal in mice, injecting them directly into the brain with small amounts of triglycerides. They then observed a change in rodent behaviour. Their level of physical activity and motivation to get a treat has decreased. "The mice seemed to be satisfied with the food they ate and thus regulated their diet. In addition, the satisfaction obtained by the good meal reduced their desire to move," he explains. A little like us after a good meal....

Obese, mice no longer regulate their diet

Serge Luquet's team then carried out the same type of experiment, but in obese mice. They show that: "the triglyceride level is higher than average. And yet, "while the mouse brain, having detected these high doses of lipids in the body, should logically rebalance the diet by reducing its fat intake, the opposite is happening," he continues. "The mouse continues to eat a lot of rich foods, while remaining sedentary. »

The explanation? "As with the use of hard drugs, the brain adapts to get its reward. He can never have enough. "Does this mean that a disruption of this triglyceride detection mechanism in the reward circuit could be the cause of hyperphagic behaviours? And/or help maintain a vicious circle of weight gain? "These are hypotheses for which we currently have no answers," concludes Serge Luquet.

Eating too much fat affects our mood

Here's another reason not to eat too much fat: saturated fats affect cognitive function and influence our mood.

According to a recent study published in the journal Neuropsychopharmacology entitled "This is what happens to your brain when you eat fried eggs", a diet high in saturated fat can lead to cognitive function disorders, including blunting the dopamine reward system, while increasing dependence on overly rich foods.

The researchers worked with three groups of rats. The first group was fed a low-fat diet containing equal amounts of monounsaturated and saturated fatty acids. The second group received a diet high in monounsaturated fats where 50% of the calories came from olive oil. Finally, the third group received a diet high in saturated fats where 50% of the calories came from palm oil.

Rats on the latter diet had a significantly reduced dopamine function (a neurotransmitter that plays an important role in communication between certain neurons). In other words, the more palm oil fortified foods they consumed, the more they had to consume to achieve the same level of satisfaction.

According to the team of researchers at the University of Montréal, who led this study, it is not surprising that what we eat has a profound impact on brain function. Their study shows that, regardless of weight gain and the risk of cardiovascular disease, a diet high in fat can cause deficiencies in the functioning of the brain circuits deeply involved in mood disorders, drug addiction and overeating.

"Consumed reasonably, fatty acids are not dangerous but they should represent a small percentage of our diet," they explain.

In which foods do you find omega 3s?

Omega 3s are essential fatty acids for the body. Excellent for the heart, brain, fetal development during pregnancy, they are the allies of a balanced health. Our diet is also our biggest source of omega 3 and if we immediately think of fish, it is far from being the only source! Here's how to refuel.

Our body's need for omega-3

According to the WHO, an adult should consume about 2g of omega 3 per day. Humans, if they are not able to produce omega 3, nevertheless have the ability to synthesize it thanks to an intake of alpha linolenic acid, also known as ALA. There are therefore direct sources of Omega 3 and those, which could be described as indirect, which provide us with this acid. Plant sources will only provide the precursor to the body, while animal sources will provide us with the "finished product", called DHA or EPA.

Omega 3 oils and vegetable sources

Rapeseed oil, linseed oil, walnut oil, soybean oil and cod liver oil are the most generous oils in omega 3. But they only provide ALA, so they must be consumed in large quantities to obtain a satisfactory quantity. Omega 3 is also found in spinach, lentils, salad and leeks.

In fact, to fill up with alpha linolenic acid, you must consume products from animals, but eat a diet rich in omega 3. Because if the animal eats well, so does the human being! There is currently a return to a more natural diet for farm animals, which is fed with plants and seeds rich in omega 3 such as alfalfa, lupin, peas, flax or faba beans.

Fish: king of omega 3s!

Some populations that consume large quantities of fatty fish are less affected by cardiovascular disease than Westerners. An imbalance that owes nothing to chance! There is a particularly high concentration of omega 3 in salmon, mackerel, herring, albacore tuna, sardines and hake, also known as hake or place.

Nuts: caloric but rich in omega 3

Nuts are excellent sources of omega 3, but they should nevertheless be eaten in moderation because they are high in calories. Nuts, hazelnuts, almonds and pistachios are particularly recommended. It goes without saying that it is better to buy them plain and unsalted!

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