carbs, metabolism, cardio vs strength, and getting lean

A great article to read, and worth the read for everyone looking to be successful in their exercise and dieting.

1. The Carb energy vs Fat energy issue is not merely just about long vs short duration. It is about a figured called VO2 Max, and all the studies done on VO2 max as a correlative to fat or carb utilization revolves around a handful of studies showing that ACUTE fat burn is elevated via lower VO2 max (long duration cardio) vs high VO2 max. But the debate has always be fueled by the fact that we are not always thinking of fat burn in the acute phases, rather, the residual effects of a high VO2 max exercise has a carry-over metabolic stimulus. As to your question, yes she makes a great leaping assumption: that you have not been eating low carb for an extended period of time. If you are in a state of ketosis, the body will in the short term look to ketones as a viable energy source. However, I can see why she made that assumption, as the author clearly views people on low carb as "uneducated"....this is a stance I share as well. Carbs are optimal for energy. Better than ketones, more bioavailable, and less "expensive" to store.

2. This depends wildly on the extend to which you want to "lean out". If I want to get into contest shape, at some point, I will have to glycogen deplete. It's much easier to glycogen deplete if you limit the amount of carbs you eat. But people should understand that this is not a "normal" undertaking. It's for those that want to be ripped to shreds, and risk muscle loss to get that super lean look. I disagree with the "expense" of converting carbs to adipose. It's far more "expensive" to convert protein to ketone. Carbs are easily stored as fat in a sedentary environment, or for those that are insulin insensitive. But since athletes and those with a high level of fitness usually are extremely insulin sensitive, yes, carbs are optimal in a weight loss progression scheme. Think of the Michael Phelp's 14,000 calorie daily diet. Look at how lean he is. But it "takes work" to lose weight with high levels of carbs, so work output must match intake. In my personal view, I think this is the most rewarding way to lose weight...it's certainly not a "lose 10 lbs so i can go to the beach" kind of mentality.

3. The acute metabolic fat loss implications of lifting are quite dependent on variables like rest time between sets, total volume, total poundages, rep schemes, and rep cadence may play a role in how much you burn while lifting. If you manage to keep your heart rate elevated for the total of 1.5 hours during a workout session, that's technically cardio + weights (wouldnt you agree?) But let's say for the sake of argument that we have a low heartrate and are just moving moderate to heavy poundage in a low rep set scheme. What are the residual fat loss effects of lifting heavy? First, and the most obvious is the caloric expenditure required to recover your muscles after a load bearing workout. For your body to heal itself and grow stronger is a caloric feat in itself. To shuttle nutrients and proteins and sugars and fats to the places they have become depleted takes a great caloric toll. As opposed to a marathoner who runes 10 miles, there is no real neuro-muscular recovery required. Instead, all he or she must do is refill her glycogen stores. Secondly, since lean tissue requires calories to maintain, your resting metabolic rate will increase by default. Holding more muscle is basically passively increasing your ability to burn fat. Thirdly, the ratio of muscle to fat is an indicator of bodyfat. If I hold 20 pounds of fat currently vs 80 pounds of lean tissue, and all things staying the same, suddenly gain 20 pounds of lean tissue, my bodyfat % has just dropped wtihout technically losing ANY fat. Add that to the two other benefits above, and you have a trifecta of reasons why lifting may be your better strategy.

Just my two cents!

Yep... she's my coach.

Nice!

Pretty good article. Could be better without the explicits, but to each their own.

I read this yesterday and liked the gist of the article. It's not a short or easy read, but there is some really good info. It's geared a bit towards women, but applies to everyone. Definitely worth the read.

http://www.fitnessbaddies.com/why-lifting-weights-lets-you-eat-more-carbs-and-all-about-metabolism/



Now, after thinking about it a bit overnight, a few questions have arisen...

1) Early in the article she talks about how everything affects everything else, which I like because I agree with it. You can't look at things or talk about things in a vacuum. However, she goes on to talk about fuel for workouts, and how carbs are a primary fuel source for short duration/high intensity efforts (HIIT, lifting, etc), and that fat is a primary fuel source for longer, more moderate efforts (steady state cardio). Yet, she makes no mention of recent diet/intake. Is that fair? Is it reasonable to talk about how a workout is being fueled without talking about recent intake?

It's still important to keep in mind that the "fuel" used during a workout is an acute response that will have virtually no long-term effect on stored body fat. The mix of fuel substrate used during exercise is driven primarily by the metabolic demands of the activity--first, intensity and second, duration.

Things such as training adaptations, recent diet, etc, can affect the mix somewhat. However, that will affect the acute response, not stored body fat. You can see studies in which changing some of these variables result in an RQ shift during exercise, but have no effect on 24 hour fat oxidation. (See Melanson et al, Exerc Sport Sci Rev. 2009 April ; 37(2): 93–101).

Now these "recent diet" effects can have an affect on the quality of the workout itself. Some people think that fuel substrates can be interchanged ad lib, but that is not the case. For example, someone who says they can do a full cardio workout in a fasted state is likely either: A) exercising at a relatively low to moderate intensity/duration or even in a "fasting" state, they have adequate glycogen reserves to fuel the workout. I think many people overestimate both the degree of their "fasted" state and the actual amount of energy they expend during a typical workout.

The nature of beta oxidation (fat oxidation) is such that it limits the intensity at which one can work. You can't just "trick" your body into substituting fat for carbs and then proceed like nothing changed. If one is depending primarily on fat as a fuel substrate, work intensity is limited to about 60% of VO2 max. When you see a marathoner "hit the wall", that is what is happening --they have to slow because they are depending mostly on fat at that point. Watching a marathoner slow to a crawl and stagger down the street --THAT is what a real "fat burning" workout looks like.

If someone is truly glycogen-depleted, it will be very obvious very quickly when they start to work out.

If someone has eaten a high-fat meal and has higher circulating levels of triglycerides, that will also have a negative effect on the workout--same reason, working at a lower % of VO2max.

So, in summary, recent diet and other factors can have some effect on fuel substrate usage and on quality of workout, but these are mostly acute effects, limited to the workout itself.

(Disclaimer: I don't really comment on the effects of exercise and fuel substrate utilization of those who are in ketosis. Other than the clinical implications of those who are in that state due to metabolic derangement, I have absolutely zero interest in the subject).

2) She talks about how, due to the "expense" of the process, the body does not want to convert carbs to fat, rather it prefers to burn carbs as energy and store fat. Does that then hint at a diet higher in carbs and lower in fat (relatively speaking, not talking about crazy low fat diets or stupid high carb intakes) might be more "efficient" for leaning out given appropriate exercise?


3) She talks about EPOC (the post-workout burn you get from strength training)... most people agree that it does exists, but most of what I've read suggests that it's not the holy grail many people make it out to be. She uses the analogy of 10% of a million dollars vs 50% of 10 dollars. That suggests that a smaller "burn" over a longer period of time is better than a higher burn over a shorter duration. I get that, and it makes sense... I just wonder if it's correct. From what I've read and the handful of people I've talked to about this, the reality seems to be more along the lines of a shorter but higher burn with cardio (say 500 cals in 50 minutes) vs a slower but longer burn (100 cals every hour for 5 hours)... but in the end the overall burn is pretty similar. Yet the article makes it sound like the metabolic impact of lifting is significantly greater than that of cardio.

This is still a subject on which the research is not definitive, IMO. Lyle McDonald cites a meta-analysis that suggested that high-intensity workouts had an average "afterburn" of 14% of total calories burned during exercise, vs 7% for a more moderate workout. His contention was that it was still better for obese individuals to do more moderate cardio in order to achieve a greater overall calorie burn. His examples were to compare a HIIT workout that might burn 250 calories in 20 min. Even with a 14% EPOC, total calorie burn was less than 300. That same person might be able to burn 500-600 doing a more moderate 45 min workout. I have seen that same position argued by others. I don't agree with it 100%, but I do think it provides an important perspective and counterpoint to those who believe in "all HIIT, all the time, for all people".

I think there is enough evidence out there to suggest that higher-intensity workouts do have an enhanced "metabolic" effect that extends beyond that workout time itself. But I don't think we know exactly why that occurs. There is so much political and ideological BS to wade through on this subject that I find it really difficult to find reliable information.

Limiting carbs = potential muscle loss due to decreased work output. If you're able to maintain work output in the absence of the amount of carbs you previously were accustomed to, there is the risk of overtraining the muscle and/or cortisol and stress hormones overtaking muscle maintenance. That's all disputable of course, but the theoretical implications are that even if one were to have enough total calories in the form of protein/fats, that the converstion of protein and/or fat to glycogen or ketone is in itself an inefficient route. I would wonder if this would hamper our ability to recover quickly enough to maintain the levels of intensity required to maintain work output and therefore muscle mass.

Though bottom line is you're probably right that given sufficient calorie intake no matter in which form is probably going to be enough to maintain muscle, though it's probably not the optimal way to maintain it?? if that makes sense .

As to the issue of glycogen deficiency during IF protocols, which is something I really love when cutting, I think the muscle training regimens of IF followers are low volume high load, multi-joint movements. The reason for this is on a strict IF eating schedule, assuming a morning workout, there is no way you are not glycogen deficient. Therefore, the workouts that Martin B. over at lean gains offers up (which I believe to be optimal in the case of IF), are very quick, intense, and heavy heavy. This way, you're saving the precious glycogen stores you currently have to force muscle growth in a short span of time. There is probably enough left in the tank after your workout to aid in recovery, before you get to your eating window. Also he advocates BCAAs for morning trainers to elicit some insulin response, which sorta maybe makes sense. But I have to say from my personal experience, doing IF and heavy lifting for a year, I failed to maintain the sarcoplasmic "buffness" I had when I was training more volumously and eating more frequently. I was very dense, but never looked quite as "full"...which is just a very bro concept I guess, but still hurt my ego haha.