This website, Burn the Fat Blog, has been online since 2006. There are tons of great posts buried way back in the archives that rarely get viewed anymore. While a handful of them need a wee bit of updating, most of these posts are evergreen and relevant today.

In some cases, the topics are not only relevant, but also, based on what’s going in the fitness and weight loss industry currently, sometimes we need new reminders of old lessons. That’s why I created another blog category for “classic posts” and I’ll occasionally bump selected articles back to the top of the feed. We also do “#ThrowbackThursdays” and share these posts with our Facebook group.

I recently saw an article in Alan Aragon’s Research Review about the high energy flux lifestyle and why it’s superior for health and body composition. In a nutshell, the concept is, “eat more, exercise more.” I was thrilled to read that because I hadn’t heard anyone else talk about energy flux in a long time. That took me back decades, to the time I interviewed Dr. John Berardi about this subject, which he calls, “G-flux.”

I knew this would be a perfect post to bump because a reminder to move more and eat more is very much needed today. The reason is that lately a lot of fitness coaches are telling their readers that exercise doesn’t help much for weight loss. Some are encouraging exercise for health, and the advice to keep a high daily step count is still popular. But I’ve also seen a proliferation of social feeds claiming things like, “exercise is almost useless for weight loss.” This is not accurate, especially without context, and it’s discouraging many people from getting more active.

The message to “exercise more and eat more” is one that needs to be heard again today. This approach – the high energy flux lifestyle – has tremendous benefits compared to eating less and staying inactive.  The classic post on this page was first published almost two decades ago and the lessons and conclusions are still valid today and should not be forgotten.

The G-Flux Interview With John Berardi And Tom Venuto: A Burn the Fat Blog Archives Classic. Originally published March 26th, 2007.

To lose body fat, you need a calorie deficit, which means you must eat less than you burn or burn more than you eat, whichever way you want to look at it. In a recent Blog post, we looked at a controversial study which suggested that it makes no difference which way you get your calorie deficit – whether you cut calories or increase exercise, the same weight loss is the end result. This research obviously struck a nerve because it brought in more email and more comments than any other newsletter or blog I have ever posted. Now with Dr. John Berardi, we take yet another look at the cutting calories more versus exercising more debate.

For years I have suggested that it does make a difference how you achieve your deficit. Although you can lose body fat with any calorie deficit, I believe that it’s far superior to “Burn the Fat” and create a deficit by increasing activity than it is to “starve the fat” by decreasing calories drastically with very low calorie diets and remain inactive.

However, “burning more” by increasing activity has never been a very popular idea. Most people are ok with the “eating more” part, but they shy away from the hard work and time commitment necessary to increase their level of exercise. This is clearly reflected in diet and fitness industry marketing today which often makes claims of “losing weight without strenuous exercise” or getting in top shape in “just minutes a day.”

However, a growing body of evidence supports my conclusion that more food plus more exercise is a superior approach for performance and body composition improvement. Dr. John Berardi, creator of the Precision Nutrition System, and one of the industry’s most respected nutrition expert’s and performance enhancement coaches says…

“The best bodies are always built on higher levels of physical activity.”

Dr. Berardi has developed a methodology called “G-flux” which is short for “energy flux” and simply refers to the amount of energy flowing into and out of a system… in this case, the human body.

I found the similarities to my own Burn the Fat Feed the Muscle approach and the g-flux approach to be striking, so I contacted Dr. Berardi to learn more and was pleased to be granted one of the most in depth interviews on G-flux that has been published to date. Because of the length, this interview is split into two parts.

The G-Flux Interview With Dr. John Berardi, Part 1

Tom Venuto: John, Thank you for the interview. I’ve been following your work for years, but the first time I heard you talk about “energy flux” or “G-flux”, it really got my attention and I said to myself, “He is right on the money with that one!” It fell right in line with my experiences as a bodybuilder and with what I’ve been teaching my clients.

I have a fat loss program called Burn the Fat, Feed the Muscle , which suggests that it’s better to exercise more (burn) and eat more (feed) than to try to lose fat by eating less and exercising less. Are we talking about the same concept here essentially, and if so, what are some of the biggest benefits of this approach?

John Berardi: Well, first of all, it’s an honor to speak with you and to do this interview! I’m a huge fan of your work too!

Secondly, you’re right on track with the exercise more/eat more thing. In fact, that’s exactly what G-Flux is all about.

(Of course, we’re assuming here that the additional exercise is done properly and the additional food comes from the right sources.)

The amazing thing is that by increasing G-Flux, even in energy balance (where calories in theoretically equal calories out), people see increases in sympathetic nervous system activity and metabolic rate. And these increases lead to increased lean mass and decreased fat mass. Again, even in energy balance.

Now, this can get confusing so here’s an example.

Take an individual eating 2000kcal a day and burning 2000kcal a day. That person wouldn’t likely lose or gain any weight. They’re in energy balance and that means they’d be weight stable.

Yet if we use the principles of G-Flux to boost this person’s food intake to 3000kcal a day and boost their calorie burning to 3000kcal a day, most would assume that the person wouldn’t change. They’d assume that the increased intake and expenditure would cancel each other out, right.

But researchers have shown that in such a situation there are increases in metabolic rate, losses of fat, and increases in lean mass! The weight might not always change but body comp certainly does. And that’s the power of G-Flux! Eat more, exercise more, build a better body.

Tom Venuto: One thing I want to clarify is that when we recommend eating more to optimize performance, metabolism and fat loss, we are not talking about simply eating larger and larger amounts of food at the same activity level and expecting our metabolism to continue increasing to match that, are we?

I remember some gurus in the body building world who recommended that bodybuilders should eat outrageously large amount of calories based on this premise. One in particular back in the early 1990’s was suggesting up to 4,000 calories a day for women and upwards of 8,000 calories per day for men. That sounds like a prescription for fat gain to me.

With your model of G-flux, aren’t you referring to eating more at a higher, but manageable level, while also exercising more at the same time? This way, for fat loss we can still have a deficit, and for muscle gain we can still have a small surplus, but in both cases it would be at a higher level of energy expenditure?

John Berardi: You’re right, G-Flux is not about simply “eating more to boost metabolism”. Flux means flow and we’re talking about energy flow into and out of the body. So G-Flux covers both the intake and expenditure sides of the equation.

In essence, G-Flux is about exercising more so that you can eat more and all the while improve metabolism, lean mass and body fat %.

At this point, let’s get real practical. There are essentially 2 steps to increasing G-Flux:

Step 1 – Increase calorie expenditure through specific exercise strategies that include a mix of strength training, interval exercise, and low intensity exercise/cardio.

Step 2 – Increase calorie intake to:

a) Match this energy expenditure if you want to maintain your weight yet improve your body comp
b) Fall just below energy expenditure if you want to lose weight while improving metabolism and lean mass
c) To exceed energy expenditure if you want to gain weight while improving body comp
G-Flux is pretty much that simple!

Tom Venuto: G flux sounds to me like the antithesis of CRON or calorie restricted optimal nutrition, which some people practice believing it will extend lifespan. In your discussions of G-flux, does this subject of life extension through calorie restriction ever come up from your readers or audiences and what is your response or criticism?

John Berardi: Oh yeah, I hear this ALL THE TIME.

Some believe that calorie restriction is the only way to enhance lifespan in humans. And to them it seems that the opposite – high levels of G-Flux – will shorten lifespan. Sure, this at first sounds logical. Yet as my grad school buddies always said, just because it’s logical doesn’t make it physiological.

Yes, many animal models have demonstrated that reducing calorie intake by 30-50% can dramatically increase lifespan. But before dropping your calorie intake by 30-50%, consider the following.

First, there are a lot of questions left unanswered. Just a few, for example, are:

Do all these animal studies translate to humans?

Are there other ways to live longer vs. eating 30-50% less?

How exactly does calorie restriction work and can we mimic that other ways?

Are there any risks associated with eating this much less?

These are big questions that shouldn’t be dismissed!

Second, the current comparisons between a “typical” diet for animals and a calorie restricted one aren’t fair comparisons. After all, typical rat chow or monkey chow isn’t exactly healthy. It’s not even real food. Rats, for example, are fed chow pellets – in essence, processed, fast food! So they’re not eating all that healthy in the first place.

What if they were actually fed a healthy higher calorie diet vs. a healthy lower calorie diet? What if they ate the equivalent of 5-10 servings of fruits and veggies a day? What if they exercised regularly? What if they supplemented with fish oil? What if they maintained low body fat? And so on…

I speculate that if these animals were given the chance to follow a healthy diet and a high level of G-Flux, the effects of calorie restriction wouldn’t seem all that impressive.

Translated to humans, here’s what I think. If you’re going to keep up your typical North American, low quality, high sugar, processed diet while refusing to exercise, then yes, calorie restriction might help you live longer. But that’s a choice that no one has to make.

In the end, eating well, supplementing intelligently, and subscribing to a life-long exercise program may prove to be more powerful than calorie restriction. And you won’t have to suffer the psychological perils (restriction, deprivation) or physical perils (below) associated with this approach. That’s right; there are some health problems associated with calorie restriction.

Mike Linksvayer, the example of a calorie restriction proponent detailed in a recent New York Times article, stands 6ft tall and 135 lbs. Mike is severely underweight. Now, that might be better than being overweight. Yet this low body weight presents its own risks as he ages.

Studies show that those with low body weight and low muscle mass are at a higher risk for a loss of independence into their elder years. This is due to the natural losses in bone and muscle that occur with age. So Mike may be healthier than his friends now, but watch out Mike as you age!

So, in the end, don’t stop eating just yet. Although calorie restriction works in animals, it’s not yet proven in humans. And if it does turn out to work, who cares? Calorie restriction is so difficult and carries its own risks including exchanging quality of life for longevity.

Why not learn the good lifestyle habits associated with smart eating, proper supplementation, and lifelong exercise? That way you can eat, exercise, and be merry while living long and living well.

Tom Venuto: We know that metabolic rate is dynamic and not fixed, and that with starvation, metabolism can slow down to a greater degree than what is accounted for by the decrease in body mass alone. This is known as “metabolic adaptation.” But what about in the other direction? Does metabolism really increase that much with an increase in food intake alone? Is it technically correct to say that eating more increases metabolism or would it be more accurate to say that eating in the optimum amount prevents metabolism from slowing down? Or, are both statements true?

John Berardi: I’ll have to answer this question with the dreaded “it depends” response. Here’s why.

There is a small % of the population who actually can up regulate metabolism by simply overeating. Studies by Levine and colleagues have shown that some folks, even when keeping exercise the same and overeating by 1000kcal per day for 8 weeks, will gain very little weight because their metabolisms just ramp right up when eating more.

Yet this isn’t true for everyone. Different subjects in the very same study responded very differently to eating an extra 1000kcal per day for 8 weeks.

Some subjects, those who don’t up regulate metabolism when eating more, gained as much as 15lbs of fat during this time! And others, those who do up regulate metabolism when eating more, gained as little as 1lb of fat! I’m sure those who gained the 15lbs were ready to crucify the others by the end of those 8 weeks!

So, it does depend…it depends on whether you’re an ‘up regulator’ or not. If you are, you do get a big metabolic boost by eating more. If you aren’t, you don’t.

Yet, I don’t recommend rolling the dice and eating an extra 1000kcal per day, hoping you’re one of those metabolic up regulators. After all, if your goal is to boost your metabolism, it’s likely that you’ve got some fat to lose. And if this is true, it’s likely that you’re NOT a metabolic up regulator. So your best bet is to approach your fat loss in two steps as discussed above.

Step 1 – boost the exercise.

Step 2 – boost intake.

Tom Venuto: For fat loss, we know we need a calorie deficit, but you can have a deficit at a high energy intake or a deficit at a low energy intake. For example, you could have a 750 calorie deficit by consuming 1500 calories a day at an energy expenditure of 2250 calories per day. Or you could have a 750 calorie a day deficit at an intake of 3000 calories per day with an energy expenditure of 3750 calories per day. That’s a pretty big difference in activity and double the food intake. Will there be a difference in body composition results between these two regimens? And if so, how do you explain that two 750 calorie deficits have different effects in light of the laws of thermodynamics?

John Berardi: The whole goal of increasing G-Flux is boost total metabolic rate and, if fat loss is required, to allow you to eat more while still being in a negative energy balance.

Simply put, it allows you to diet at 3000kcal a day vs. 1500kcal a day (as per your example above). And personally, I MUCH prefer this!

You see, by allowing you to eat more while still being in a negative energy balance, the principles of G-Flux lead to the following benefits:

  1. Increased total food intake when dieting, a powerful psychological benefit.
  2. Increased micronutrient and phytochemical intake, leading to better function and better health.
  3. Increased sympathetic nervous system activity, leading to a faster metabolism.
  4. Increased nutrient partitioning, leading to less fat and more muscle

Tom Venuto: What about the scientists who say there’s no difference between a deficit created by calorie restriction and a deficit created by increased activity? For example, what are your thoughts on the recent highly publicized study by Ravussin, which suggested that “diet or exercise both reduce weight equally?”

John Berardi: Big in the media lately is the idea of “debunking” everything, including time-tested exercise and nutrition protocols.

To this end, they’re taking some recent research showing that calorie restriction alone and calorie restriction plus exercise (aerobic, mind you) are equivalent for weight loss and using it to promote some mixed and odd messages.

These messages are based on this one study so I’d like to comment on it here. Here’s the study.

Title: Effect of calorie restriction with or without exercise on body composition and fat distribution.

Conclusion: Exercise plays an equivalent role to calorie restriction in terms of energy balance; however it can also improve aerobic fitness which has other important cardiovascular and metabolic implications.

Media Take: Either eat less or exercise more, there’s no need to do both.

My Thoughts: There’s nothing surprising about this study. Controlling energy balance is the key to body weight change. Whether it’s strict diet alone (one condition in this study) or moderately strict diet + cardio (the other condition in this study) doesn’t matter.

And while this study has merit, it’s not the definitive answer on whether one should exercise or diet to drop weight. After all, the health benefits of exercise aside, this study doesn’t include weight training or interval exercise interventions.

Any trainer or exerciser worth his or her salt knows that it takes food control and a diversified exercise profile (weights, intervals, cardio) to promote the best weight and body composition results in both the short term and long term.

To support my thoughts, here’s a review of the literature:

Title: The effects of exercise training on fat-mass loss in obese patients during energy intake restriction.
Conclusion: The implementation of resistance training in such programs does not augment fat-mass loss but improves body composition by increasing fat-free mass. Further studies are needed to define the optimal interventional program for obese patients.

My Thoughts: This review supports the notion above suggesting that a negative energy balance, whether it comes from cardio or diet alone, is the most important factor for weight loss.

However, when resistance training is added, LBM is preserved while the fat mass is lost – a huge long-term benefit that neither cardio alone, nor energy restriction alone, nor cardio plus energy restriction offers.

In the end, all these positive interventions have a place. Controlled energy intake, low intensity cardio, resistance training, and high intensity interval work should always find a way into your or your clients’ programs.

Tom Venuto: If somebody decides to just eat less and not exercise, which is the case for many popular diet programs, what is the impact on performance, metabolism and body composition short term and also long term?

John Berardi: Well, for starters, choosing not to exercise is a huge mistake for anyone, regardless of their goals. The human body was built for exercise and, over time, has developed with exercise as a survival necessity.

Yet nowadays exercise has become unnecessary for survival and, on the whole, our society has become sedentary. This has lead to huge health and body composition problems.

Plain and simple, it’s a fool’s choice not to exercise.

Yet let’s say someone simply won’t exercise. In that case, eating less (while still eating well) is certainly better than eating whatever they feel like, whenever they feel like it – which will usually lead to over feeding and under nourishing.

However, assuming the no exercise, low calorie scenario, problems can still develop. For starters, muscle and bone mass will likely be lost. This means long-term problems like osteoporosis and sarcopenia. In other words, get ready for the nursing home.

Also, metabolic power diminishes. Eating less while not exercising is like rapidly down shifting the metabolism. And this means that when the “diet” ends, it’s quite easy to gain fat.

In the end, the body finds it very hard to balance energy intake and output when sedentary. So even if you try to under eat your energy expenditure, if you’re not exercising, you’re likely losing muscle and losing metabolism throughout your diet. So you’d have to continually drop calories in a never-ending downward spiral of muscle loss, metabolic loss, and calorie deprivation. This is a battle most can’t win!

The beauty of high levels of G-Flux is that when the body is very physically active, it tends to find new energy balance points without rigorously counting calories, etc. Therefore it’s easier to be in great shape when G-Flux is high. In my seminars I devote an entire section to this idea – improving body composition without counting calories.

Tom Venuto: Knowing that metabolism will decrease with a calorie deficit, but that we have to restrict calories to lose fat, what are the best ways to get around this conundrum? I have often suggested calorie cycling or re-feed days as one approach, but it’s unclear how much a single day or two at higher calories will influence metabolism. Do you have any thoughts on this or other methods to keep our metabolisms humming along when we’re in a caloric deficit for months at a time while cutting?

John Berardi: Ultimately, when trying to lose fat, we do have to drop calorie intake to a certain extent. There’s no getting around it. So let’s say you start out burning 3500kcal a day and eating 3000kcal. Well, after you lose some weight, your daily calorie burn will be less due to the fact that you’re lighter and every activity you do costs less. So you’ll have to systematically increase your exercise or decrease your calorie intake.

But you can only increase exercise so much as there are time limitations and potential over training. So eventually calories must drop.

Yet as you mention, when calorie intake drops, metabolism may drop. And again, the downward spiral begins. However, as you mention, there are some tricks for keeping the metabolism high and fat burning maximized.

First, your exercise really has to be dialed in. Some people want to throw the entire onus on diet but exercise is really important too. You’ve got to know what you’re doing on this end, finding ways to burn more calories as you drop body fat and body weight.

Next, strategic carb cycling, as you mention, is a great way of doing so.

Finally, for the more disciplined folks, strategic macronutrient and calorie cycling is even better. To do this you basically have 3-4 types of eating days: a) low carb, low calorie; b) low carb, high calorie; c) moderate carb, low calorie; d) moderate carb, high calorie.

Based on your goals and body comp, you rotate through these days in specific ways to keep the body burning fat. And this works quite well but it’s not for everyone. In fact, I only use these advanced strategies if they’re needed (i.e. someone is starting out very lean or they’ve hit a significant plateau).

Tom Venuto: If someone comes to you and says they’ve been on a starvation diet for months and they think they’ve lost muscle and slowed their metabolism, where do they begin? Should they be cautious of raising calories too quickly?

John Berardi: In this case I use the same two steps I discussed above. First, if warranted, I increase exercise. Second, to compensate for this increase in exercise, I increase calories. This gets G-Flux really moving and ramps up the metabolism quite well.

Now, I should mention that before automatically bumping both up, I do a complete inventory of what they’re eating and what type of exercise they’re doing. This determines my approach.

For example, if someone is exercising tons already and following a starvation diet, my approach may be different than if someone is doing very little exercise and following a starvation diet.

But in general, the approach would be to bump up exercise and then bump up calorie intake.

Tom Venuto: There are quite a few methods available for calculating energy needs. Do you have a favorite method for calculating optimal caloric intake for the general population?

John Berardi: On our Precision Nutrition Forums we offer a calorie calculator that allows them to input their lean mass, activity levels, and more, and they’re given a full set of calorie and macronutrient recommendations. This calculator uses complex algorithms to arrive at the recommendations and therefore may be more complicated that I can get into in this interview.

However, here’s a fairly simple set of ranges:

For fat loss, eat between 10 and 16kcal per lb of body weight
For maintenance, eat between 12 and 18kcal per lb of body weight
For weight gain, eat between 16 and 22kcal per lb of body weight

Now, I know that these ranges are quite wide. That’s because they are dependent on activity levels. For example, if you’re sedentary, you’d stick to the lower end of the range. And if you’re highly active, you’d stick to the higher end of the range. For more details, check out Precision Nutrition.

Continued in part 2

John Berardi is a prolific author, having published over 200 popular press articles for magazines like Men’s Health, Men’s Fitness, Women’s Health, Muscle and Fitness, Testosterone and more. Berardi has also authored or co-authored numerous books including Scrawny to Brawny, Metabolism Advantage and Gourmet Nutrition and is the creator of the Precision Nutrition System.

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