Friday, 23 January 2009

Why exercise may or may not help you to lose weight.

Exercise. I hate it! I'm about as active as a Brazilian 2-toed Sloth. The problem that I had with exercise is that it made me hungry and I ended up eating more Calories than I burned by exercising. This was due to me doing it wrong! See Move More: Solutions to problems and Exercise decreases appetite.

The thing about exercise in moderation, is that it's good for health & fitness. The problem is that some people think that doing lots more is better. It ain't necessarily so. The 38 year old lady sitting near me at karaoke last night used to run a lot when she was at school. She now needs a replacement knee joint due to damaged cartilage and she had her knee wired up to a TENS machine. See A little moderate to vigorous physical activity does more than you think.

Too much early morning exercise can also make you ill, by raising serum cortisol level. High cortisol level is immunosuppressive. See Early morning exercise could make you ill. High cortisol level also causes water retention, so people who over-exercise can gain water weight. Chronically-high cortisol levels can also cause muscle loss, thin skin and osteoporosis.

Starving yourself and over-exercising makes things even worse. From WHY is the combination of high intensity and/or long duration activity a mistake when calories are being severely restricted?

"Water retention: cortisol binds to the mineralocorticoid receptor (the receptor involved in water retention, well one of them). And although cortisol has 1/100th of the effect on water balance of the primary hormones (aldosterone and a couple of others), since there is like 8000 times as much of it, it can cause a major effect."

"Excessive cortisol, especially chronic elevations cause other problems not the least of which is leptin resistance. Which only magnifies the drop in leptin from dieting. This could be another mechanism behind the greater drop in metabolic rate for the study I mentioned above."

So, what's the best thing to do for maximum fat loss with minimum muscle loss? A mixture of high-intensity exercise (resistance training with weights, or sprinting) and medium-intensity exercise (jogging) (a.k.a. High-Intensity Interval Training, or HIIT) is better than just medium-intensity exercise. See Resistance Weight Training With Endurance Training Enhances Fat Loss, Impact of Exercise Intensity on Body Fatness and Skeletal Muscle Metabolism and HIIT & Run.

One theory to try and explain the improved fat loss of HIIT is that Calories are burned after the high-intensity exercise is finished. However, the Excess Post-exercise Oxygen Consumption (EPOC) only amounts to ~35kcals, so it isn't significant. It's almost certainly the appetite-suppressive effect of exercise that makes you glow, that results in reduced Calories in.


Rosso said...

Your friend Zoe Harcombe is on this same wavelength too. I do personally like how the dietary alterations I have done have affect my cycling. I able to push it just that little bit longer up the Yorkshire Dales. I'm looking forward to the summer, my new cycle and the countryside!

Katie said...

Uh... you forgot that insulin sensitivity is increased by heavy weight lifting. Sprinting also increase hGH (growth hormone). You cannot just say that it "reduces appetite and burns calories". This might confuse some newer readers. We both know that there are more complex hormonal benefits intense exercise. And, where do you get the evidence that "cardio" and HIT (not HIIT... though intervals are in the category) are better than HIT alone?
GREAT Blog by the way!!

Nigel Kinbrum said...

Hi Katie.

I left out the other benefits of resistance training for the sake of simplicity.

I wrote that cardio and HIT are better than cardio alone.

Cheers, Nige.

Anonymous said...

I'm 1.9 meters and 109 kgs. I', afraid I might be fouling myself by cutting calories too low and doing medium intensity exercise.

I cut my calories to 2,000. I exercise about 5 hours a week at medium intensity. It doesn't seem like I'm losing anything. (I fast too 12hr+) What should I do?

Nigel Kinbrum said...


Your BMI is only just scraping 30 so you're not going to drop dead any time soon. It doesn't matter if your calories are low provided that your protein intake is sufficient to spare muscle. At 109kg, you should be eating between 109 and 160g/day protein. Also, ensure that you get enough EFAs.

Do you do any resistance-type training?


Anonymous said...

Nigel thanks,
I do resistance training at least two days, usually 3 days a week. And I briskly walk (even uphill) w/ a few weak sprints thrown in, for a total of 2hrs on the days I don't.

I've heard that your body can only assimilate 30g of protein per 2 or 3 hours. Is that true? If it isn't I'd eat a lot more protein at a sitting. It'd hit between 110-160g easier.

I get about under a teaspoon of Cod Liver Oil a day. And I eat fish a few times a few times a week. But not too much because I get acne (from n3 overload).

Nigel Kinbrum said...


It looks like you're doing the right sort of exercise.

"I've heard that your body can only assimilate 30g of protein per 2 or 3 hours. Is that true?" No. It's one of those Bro myths that's repeated so many times that it's accepted as fact. The more protein you eat, the longer it sits in your stomach being broken down by pepsin & HCl into short-chain peptides. About 95% of all animal protein you eat gets absorbed (except for raw egg white, which is only about 55% absorbed), unless you have a high fibre/fiber intake, which sweeps some nutrients through unabsorbed (usually causing severe wind!).

Whey protein on its own leaves the stomach quite quickly as it's already short-chain peptides, so there's no point in taking huge amounts of whey in one go as the body just burns most of it for energy.

n3 overload? What's your n6 intake like?


Anonymous said...

Thanks again, Nige.

A minute after posting the protein speculation I realized it didn't make sense, particularly from a historical lens. You're right.

I've noticed my acne is *strongly* correlated with total PUFA and lactose (w/o lactase) intake. So dairy is out, sans cream and butter (and cheese). I only eat butter now anyway. And I limit fish (w/skin) to only couple times a week.

In the US they sell canned Salmon (418g) which has roughly 14g of PUFA (n3s). If I eat it skin and all, the next day I'll get chest acne. Same things happens with dairy, ricotta especially (whey). PUFA above 7g kills me, whether in n3 or n6. And that makes sense because it's above 4% of calories. I even limit pork sausage for that reason. Of course I balance and limit n3s/n6s. They seemed like could stall weight loss, like too much fructose/fruit.

BTW, I think I've lost 4.5kg. But my scale is wonky. Things seem to be working.

Nigel Kinbrum said...


That's interesting about acne. I don't know much about the subject, but in youngsters, it has something to do with free testosterone levels. Apparently, even teenage girls can have high free test levels, causing spots & attitude!

So, could pufas be having an effect on your free test, via SHBG? I have no idea, but if eating too much "x" causes you problems, don't eat too much "x".

Even if your scales are knackered, if your trousers feel a bit looser around the waist, you're doing it right.

Cheers, Nige.