Aerobic exercise increases whole body adipose tissue lipolysis, but is this lipolysis higher in the subcutaneous adipose tissue (SAT) adjacent to the contracting muscle than in the SAT adjacent to the resting muscle? Ten healthy men, on an empty stomach, performed one leg extension exercise at 25% of the maximum load (Wmax) for 30 minutes, followed by exercises at 55% Vmax for 120 minutes with the other leg and finally at 85% Wmax for 30 minutes with first leg. Subjects were tested for 30 minutes between exercises. The blood flow in the SAT of the thigh was assessed using the flow of radioactive (133) Xe, lipolysis was calculated from the SAT of the interstitial thigh, the concentration of glycerol in arterial blood. In general, blood volume, as well as lipolysis, was higher in the SAT of the thigh adjacent to the muscle than in the adjacent muscle that was not working (measurement time 15-30 min after exercise: blood flow:
25% Wimax: 6.6 +/- 1.0 vs 3.9 +/- 0.8ml 100g(-1)min(-1), P<0.05;
55% Wmax: 7.3 +/- 0.6 vs 5.0 +/- 0.6, p<0.05;
85% Wmax: 6.6 +/- 1.3 vs 5.9 +/- 0.7, P > 0.05;
lipolysis: 25% Wmax: 102 +/- 19 vs 55 +/- 14 nmol 100g(-1)min(-1), p = 0.06;
55% Wmax: 86 +/- 11 vs 50 +/- 20, P > 0.05;
85% Wmax: 88 +/- 31 vs -9 +/- 25, P<0.05).

In conclusion, blood flow and lipolysis tend to be higher in the SAT adjacent to a working muscle than adjacent to a resting muscle, regardless of exercise intensity. Thus, specific exercises can induce "local lipolysis" in adipose tissue. Key words: exercise, local lipolysis, microdialysis.

Reference.
The idea of ​​local reduction has been a topic that has been circulating around the world of fitness and body recomposition for decades. Men want to consistently have six pack abs and can be seen doing endless abs exercises, women want to have lean hips and therefore do endless reps on the inner/outer thighs.

One hour "abs workout" or "butt/thighs" classes that are filled with an hour of movement for a given area of ​​the body can be found in most commercial gyms. Even in the world of bodybuilding where people really need to have the knowledge, some still since they claim that at the site of contraction of a given muscle group will help reduce fat in that particular areas.

For the most part, the voiced idea of ​​reducing local fat reduction is denied by people who are in the subject (with the exception of the occasional heretic or booksellers suggesting that this is possible). Various lines of research are cited, including showing no difference in skin folds on the hands of tennis players (who typically use one hand more than the other).
An example often used in this question is that "If there is a local reduction in fat from muscle contractions, then people who eat a lot should have skinny faces." A little silly, but I think he hits the mark. If a specific muscle group is working to reduce fat only in that area, then this is how it should work. But it's not. Or it doesn't seem to work. But, for the most part, the idea has not been directly tested, to my knowledge.
In this context, I should note as a side note that there are three major steps in fat loss that can be potentially impacted, although today's study only focuses on two. These steps are:

1 Lipolysis (actual breakdown of fat)
2 Blood flow (critical for transport when fat is broken down into other tissues for "burning")
3 Oxidation (the actual "burning" of fat in tissues such as the liver or skeletal muscle).
Could doing local activity really affect some aspect of the above in a way that would make localized fat burning or doing endless reps of localized exercises meaningful in terms of fat loss? This is where the study of this issue began: a certain effect of muscles on lipolysis and blood flow (oxidation was not measured) was compared in contacting fat cells.
And although the article was published a few years ago, but it is still circling (given as "evidence" for local fat reduction); the idea of ​​localized fat reduction is one idea that doesn't want to die. So it's worth looking at what the real or potentially real effects really are.

Study.
Using several different methods (this I'm not going to detail) to measure actual blood flow and lipolysis, the study subjects performed lower body exercises (they called it single leg extensions, but that probably means one-legged pedaling) at various intensities during rest, the other leg works. Thus, blood flow and lipolysis can be measured in comparison to an untrained leg.
This allowed them to compare lipolysis and blood flow in response to local exercise for the currently inactive leg. In fact this is extremely important as any type of exercise will generally have systemic effects throughout the body which will affect energy metabolism throughout the body. By limiting the exercise to one leg, the researchers were able to measure the response in fat cells close to the muscles that were working and compared this to fat in the non-working muscle to see the differences.
Exercises were performed at 25%, 55%, and 85% of maximum power output with a 30-minute break and switching legs from one intensity to another. This also acts as a control, so that the previous work does not affect the next exercise, since the leg received a long break from the previous exercise. As mentioned above, blood flow and lipolysis were compared between a working leg and a rested leg to see the difference.

Result.
As stated in the abstract above, lipolysis and blood flow were increased after the exercised leg compared to the non-exercising leg, although this only occurred in the two low-intensity exercises. At the highest intensity of exercise, no change was seen.

Before delving into specific figures, the question must be asked why this happened. The researchers proposed two possible options for their observation.
First, local changes in hormones (or synergies between changes in hormones and blood flow) are likely to be responsible, but there is a bigger question of why this would happen that researchers need to find out first. By why, I mean why the system will work the way it does in terms of improved physiological functioning.

The reason for asking this question is this: fat mobilized from a certain area of ​​adipose tissue (from the thigh) cannot actually be used as fuel on the muscle underneath it (eg in the quadriceps). The blood flow of skeletal muscle and fat cells are independent and any fat mobilized from the neighboring area will enter the local area. circulation and again, it cannot be used directly on this muscle.
Since there is no really logical physiological reason that the work of this muscle will cause the mobilization of fatty acids, the muscles cannot use them. Of course, physiology does not have to follow a certain logic in its work, and concern about why this is observed can make you miss the main point.

In this regard, the researchers note that there is no indication that these results actually lead to a decrease in locally controlled fat stores, stores can simply be replenished after exercise. They didn't measure post-workout fat storage, a process that happens quite often, this is fatty acid returning to the site of fat mobilization that hasn't been burned elsewhere in the body. In some extremely rare cases, fat mobilized in one area of ​​the body can be reclaimed in fat cells elsewhere.

The researchers also speculate that localized temperature increase may also affect blood flow, this has also been implicated in the weighted response. Cold tends to cause vasoconstriction and heat tends to cause vasodilatation, so there may actually be some logic to these rubber bands, i.e. to warm up the surface before training.
In any case, for whatever reason, through some mechanism, working the muscles for 30 minutes at low to moderate intensity did increase lipolysis and fat entry into the bloodstream.

Aha! Localized fat burning is possible, right? Hold on.
While it is clear that local exercise did have an effect on fat cells by increasing lipolysis and blood flow, you may notice that something I have left out of the above is an actual quantitative effect. That is, how much excess fat is actually mobilized for fuel and potentially usable.

Referring to that same study, based on changes in blood flow and lipolysis, the researchers calculated that during 30 minutes of local exercise, 0.6-2.1 milligrams (one milligram is one thousandth of a gram) per 100 grams of adipose tissue was mobilized adjacent to the contracting muscle.

Let me put it in context. First of all, let's assume that you are carrying a whopping 5 kg (11.1 pounds) of body fat in a certain areas.
If local exercise can mobilize 0.6-2.1 mg of fat from 100 grams of total fat mass next to which the muscle works, then:

0.6-2.1mg/100g * 1000g/kg * 5kg = 30-105 milligrams of fat.
Or 0.03-0.1 grams of excess fat mobilized within 30 minutes of activity.
Now, one pound of fat contains about 400 grams of fat, so our hypothetical 11.1 pounds of fat contains 4440 grams of fat. And 30 minutes of local exercise mobilized no more than 0.1 grams of fat. Wow. You will be cutting fat for about 1000 years at this rate.

Summarizing.
As far as I can tell, this should be death music for the idea of ​​localized fat loss. Yes, there