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May-26-2011

Is Targeted Fat Loss Possible?

Is it possible to lose fat in specific areas by local manipulation of that area? For example can you lose fat from flabby arms, or belly fat by doing specific exercises for that area, or applying wraps, doing massage, or just visualizing that fat away?

 

Massage, applying wraps, saunas, visualization, and other non active means of fat reduction don’t make much sense. After all unless you’re significantly increasing the demand for fatty acid oxidation, I can’t see that there would be a real increase in fat breakdown (lipolysis). I also can’t see that anyone with even a modicum of common sense thinking that they can lose body fat using these methods.

 

On the other hand spot reductions in subcutaneous fat through exercising the local muscles has been a controversial subject for as long as I can remember.

 

If you asked me that question several years ago my answer would have been that it’s unlikely that there would be much increased fat loss in fat overlying exercised muscle because I felt that fat loss is a whole body phenomenon.

 

Since most people are concerned about belly fat I also would have told you that doing abdominal exercises isn’t going to decrease your belly fat unless you cut out the jelly donuts and/or beer, and hit the weights and/or cardio involving the whole body.

 

And I would have added that sticking to a low carbohydrate high protein diet, and even better my phase shift diet, would be the best diet(s) to follow to get rid of body fat and improve over all body composition. This has also been shown to be true in several studies. The most recent of which found that an energy restricted high protein diet coupled with resistance training achieved greater weight loss and more favorable changes in body composition (see abstract below).

 

After all numerous studies have found that when you diet and exercise you lose fat all over, although you lose fat in some areas more than others but that’s due to whole body dynamics and genetics rather than secondary to an interaction between working muscles and overlying fat.

 

For example with dieting and training visceral fat, the fat between your abdominal muscles and your back bone, can be one of the first fats to be affected, although the amount you lose in this area will vary depending on your genetics.

 

While all of that’s still true, my opinion on targeted fat loss has been changing over the years and I now believe that you can target fat loss, or at least increase local fat loss say in the arms, chest, abdominal and other areas while you’re trying to lose weight and/or improve body composition, and thus augment the local and overall fat loss effects of diet and exercise.

 

There’s was never any doubt in my mind that fat in the muscle cells themselves, called intramuscular triglyceride or intramyocellular triacylglycerol (IMTG) or the intermuscular fat, the fat between muscle fibers which gives meat its marbelling effect, is used by the local musculature. But in general these aren’t the fats that most people want to lose, although in non athletes both can contribute to insulin insensitivity and metabolic disorders). What they’re looking to lose is the subcutaneous fat that makes their arms look flabby or that hides their six pack from view.

 

This subcutaneous fat lays on top of muscle and as such isn’t fat that is inside or in close proximity to the muscle fibers. On the other hand it is close enough to exercised muscle that it seemed to me that it had to be affected to some degree. After all blood flow to the exercised area increases with exercise and this includes the overlying fat.

 

And looking at it in practical terms it seemed to me that the body would use local energy sources to ones further away. That is it would use the fatty acids from subcutaneous fat overlying the muscle that’s being exercised more than fat in areas not being exercised.

 

As such, it makes some sense that say doing abdominal exercises would increase the breakdown and use of local belly fat by the underlying exercising abdominal muscles. You would also expect an increase in breakdown of fat in the whole body but this would be less pronounced than the nearby fat.

 

There’s no doubt that exercising muscle uses proportionally more fat as an energy source than muscle that isn’t being exercised, at least that’s the case the majority of people since they follow a high carbohydrate diet and thus are carbohydrate adapted. This is not necessarily the case in those that are on low carbohydrate diets or my phase shift diet that are fat adapted. In these cases exercising muscle would definitely burn more fat in total since these muscles need more energy but wouldn’t necessarily be burning proportionally more fat, just more fat than if the muscle wasn’t being exercised. This is a fine point that we’ll pursue in future issues of this newsletter.

 

For example a paper published in 2007 (Helge JW - see below) found that “During exercise respiratory exchange ratio was lower in FAT (0.86 +/- 0.01, 0.83 +/- 0.01, mean +/- SEM) than CHO (0.96 +/- 0.02, 0.94 +/- 0.03) and in UT than T legs.” What that means is that the muscles of the leg being exercised burned more fat than the leg that wasn’t being exercised. This study however, didn’t look at and thus didn’t show that the exercised leg burned more local subcutaneous fat than the non exercised leg.

 

After looking all over my own databases, Pub Med, and the Internet I didn’t find much to support what I thought might happen to local fat overlying exercised muscle. All the studies I found didn’t support the increased use of local subcutaneous fat by exercised muscles. Instead the general consensus seemed to be that it was system wide influences secondary to exercise and/or diet that regulated fat breakdown.

 

Some of the studies addressed the use of intermuscular adipose tissue (the fat between the muscle fibers themselves – think of the marbling you see in red meat) by exercising muscles.

 

And some addressed the use of IMTG as an immediate energy source. IMTG are wrongly interpreted as a sign of insulin resistance but instead should be looked at as an extremely important source of energy in athletes. I’ll be covering IMTG in detail as to their dynamics and importance to athletes, in the next issue.

 

Searching the Internet was misleading and repetitive with many hits mimicking each other and quoting a study that was supposedly published in 1984 about how abdominal exercises did not increase the breakdown of subcutaneous abdominal fat over other subcutaneous fat.

 

Regardless of whether this study exists or not I did finally find a seminal study published in 2007 (Stallknecht B – see below) that for me definitively shows that exercising muscle does have an effect on local fat and especially the subcutaneous fat adjacent to the muscle. The study concluded that “an acute bout of exercise can induce spot lipolysis and increased blood flow in adipose tissue adjacent to contracting skeletal muscle.”

 

What this means is that you can reduce subcutaneous fat over a specific area in your body by exercising the muscles in that area. For example if you want to reduce abdominal fat it’s useful to do abdominal exercises.

 

However, keep in mind that, even though this study found that blood flow and lipolysis are stimulated more in adipose tissue adjacent to contracting muscles than in adipose tissue adjacent to resting muscles, whole body exercise, whether aerobic or RT, will result in more overall body fat loss than working local muscle groups.

 

Bottom Line: More body fat will be lost overall with whole body workouts but by adding regional body exercises you can increase the fat loss even more in that area.

 

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Am J Physiol Endocrinol Metab. 2007 Feb;292(2):E394-9. Epub 2006 Sep 19.

Are blood flow and lipolysis in subcutaneous adipose tissue influenced by contractions in adjacent muscles in humans?

Stallknecht B, Dela F, Helge JW.

Department of Medical Physiology, The Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. B.Stallknecht@mfi.ku.dk

Aerobic exercise increases whole body adipose tissue lipolysis, but is lipolysis higher in subcutaneous adipose tissue (SCAT) adjacent to contracting muscles than in SCAT adjacent to resting muscles? Ten healthy, overnight-fasted males performed one-legged knee extension exercise at 25% of maximal workload (W(max)) for 30 min followed by exercise at 55% W(max) for 120 min with the other leg and finally exercised at 85% W(max) for 30 min with the first leg. Subjects rested for 30 min between exercise periods. Femoral SCAT blood flow was estimated from washout of (133)Xe, and lipolysis was calculated from femoral SCAT interstitial and arterial glycerol concentrations and blood flow. In general, blood flow and lipolysis were higher in femoral SCAT adjacent to contracting than adjacent to resting muscle (time 15-30 min; blood flow: 25% W(max) 6.6 +/- 1.0 vs. 3.9 +/- 0.8 ml x 100 g(-1) x min(-1), P < 0.05; 55% W(max) 7.3 +/- 0.6 vs. 5.0 +/- 0.6 ml x 100 g(-1) x min(-1), P < 0.05; 85% W(max) 6.6 +/- 1.3 vs. 5.9 +/- 0.7 ml x 100 g(-1) x min(-1), P > 0.05; lipolysis: 25% W(max) 102 +/- 19 vs. 55 +/- 14 nmol x 100 g(-1) x min(-1), P = 0.06; 55% W(max) 86 +/- 11 vs. 50 +/- 20 nmol x 100 g(-1) x min(-1), P > 0.05; 85% W(max) 88 +/- 31 vs. -9 +/- 25 nmol x 100 g(-1) x min(-1), P < 0.05). In conclusion, blood flow and lipolysis are generally higher in SCAT adjacent to contracting than adjacent to resting muscle irrespective of exercise intensity. Thus specific exercises can induce "spot lipolysis" in adipose tissue.

 

Full paper at http://ajpendo.physiology.org/cgi/reprint/292/2/E394.

 

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To Crunch Or Not To Crunch by Carl Lanore at http://twit2fit.ning.com/profiles/blogs/2213300:BlogPost:907.

 

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