Dr. Marc Hellerstein of the University of California, Berkeley is a fascinating person introduced to me by Chef AJ. Dr. Hellerstein is a world-renowned expert on de novo lipogenesis (DNL), the synthesis of new fatty acids. He and I have had some interesting correspondence which he said I may share, and it all makes a lot of sense. He was gracious enough to review my post and make some adjustments. Dr. Hellerstein does emphasize that there are no free calories. In his words, “it’s just arithmetic.” In my words, “calories count, whether you count them or not.”

Before getting into it, I get a lot of kick-back from some whole food plant based people who insist you do not have to count calories in order to lose and control weight. So I want to clarify once again: I acknowledge that many people do not need to count calories. They get along fine just keeping to the left of the red line in the calorie density chart. When I say that calories count it does not mean you must count calories.

That said, there are also many people like me who find they really do need to track their calories. I could not have lost as much as I did by simply minding calorie density. I know I’m not alone on this. Look at all the comments in my recent interview with Chef AJ (over 27,000 views so far!) – there are many other people who experience the same thing. Also read about Calorie Density, Average Calorie Density, and Total Calories. All I’m saying is that whether you count calories or not they make a difference in weight loss and control.

Please note that I have lost half my weight eating WFPB. See https://lerner.net/milestone-more-than-half-of-me-gone/. I am no longer obese, for the first time in my adult life. My HbA1c has dropped from a dangerously high 11.8 to a perfectly normal 5.1 and I’ve been off all blood sugar meds for 3 years now. My BMI is down to 21.3.

I was discussing this with Chef AJ and also Dr. Doug Lisle, and Chef AJ pointed me to an interesting interview she had with Dr. Hellerstein. In the interview it seemed to me Dr. Hellerstein was also saying that calories do count, and that carbs to some extent can get stored as fat, and you can’t just ignore them. So I followed up with him, and he was kind enough to reply and clarify. Here is what he told me.

Q. My discussion with Chef AJ is about calories. I think they count. She thinks just calorie density, not total calories, is what’s important. She pointed me to your interview and it seemed to me you were saying that calories do count, and that carbs to some extent can get stored as fat, and you can’t just ignore them.

A. You are 100% right about what I said and believe to be the case.

Q. My question is does that mean you can eat unlimited starch and not add to body fat? At 8:00 minutes you say, “don’t confuse that with thinking carbs are free calories.” And you say that while most of the extra carbs don’t get stored as fat, they can keep your body from burning fat. At 8:37 you say, “If you eat carb calories they are not free calories.” You repeat that a couple of times in the interview. At 9:00 you say, “There’s no place to store carbs.” That’s where you explain that the excess eventually gets stored as fat, which the body can store lots of.

A. Your interpretation is right. It’s important to have a common sense physiologic explanation, though – which I think can be made fairly intuitive. We can frame it this way:

If you had a bank account with dollars in it,
But you earned both dollars and Euros and could spend either dollars or Euros in your daily life,
Although no bank in town would exchange Euros into dollars,
Would earning extra Euros add to dollars in your bank account?
Of course they would! You’d use Euros at the grocery store and put more dollars into your bank account.
This is basically what carbs do for body fat. Your body uses them for daily needs and does not have to use fats. Which then build up as added fat in fat stores.
That’s the “arithmetic” part.

Q. Then you go on to say exactly what I always say. To lose weight you have to be in a calorie deficit. In your words, “It’s just arithmetic.” The way I put it is, “Calories count, whether you count them or not.”

A. Well put!

Q. And you do talk about complex carbs versus simple carbs (i.e. sugars versus what you get in whole foods) and that all makes perfect sense as well.

A. Especially in context of whole foods and plant-based foods – which not only include lots of complex carbs but also other volume – fiber, water, etc. The idea being that the complex carbs/whole foods are more satiating or just harder to over-eat. Appetite is where it is not arithmetic but very complicated physiology – what satisfies one person but not another? We are currently very bad at figuring this out in advance.

Q. Anyway, my ultimate question is do you think it’s possible to just eat as many whole food carbs (e.g. Japanese sweet potatoes and bananas) as you want all day and never worry about adding body fat and gaining weight over time?

A. I think anything is possible – let’s not underestimate the creativity of people when they really want something (nicotine, suppression of hunger, love) .
But it’s a hell of a lot harder to do. I’d like to see better studies asking exactly what you just asked.
My overview is that most active human beings eating foods that are not calorie dense will find it hard to gain a lot of weight. It is even likely that this behavior will lead to a more effective food “appestat” – where hunger is turned off when the body senses enough calories to fill up the tank. But the latter statement is not proven.

Q. If I don’t limit certain high calorie starches and fruits I start gaining weight. Dr. Doug Lisle says, “Oh, that’s just glycogen storage.” But you can’t just store glycogen forever, right? It has to go somewhere? I suspect conversion eventually to fat.

A. Nice question! There is an element of glycogen storage, which really means water being stored with glycogen. But that does not increase for too long – as you say.
How much weight do you gain with high calorie starches and fruits? I wouldn’t be so confident that it is glycogen if it is more than a few pounds.
Again. life is not exactly simple.Those high calorie foods might stimulate your appetite or your preference for sweetness itself (when you do this – maybe not when someone else does).

Q. But what does your research show?

A. Well most of this is pretty standard metabolic thinking, not discovered by my research. The finding that carbs don’t easily get converted to fat but can still add to body fat stores and metabolic complications was advanced by my work.

I think the punch-line here is that carbs are not free calories at all. They will allow fat to build up. But eating certain types of carbs – as you seem to be doing – might allow some people to eat fewer total calories, thereby allowing more body fat to be burnt. Which you seem to understand very nicely.

Finally a overall technical explanation from Dr. Hellerstein:

Remember, It’s not that 10% of carbs eaten get converted to fat. It’s that 10% or so of fat in your body came from carbs (or other non fat sources like ethanol).

You ask what happens to carbs if they are above this 10%? The answer is again arithmetic, but a bit more complicated. If you eat excess carbs that fills up all available storage capacity for carbs in your body, then it will:

(1) First be burnt for fuel and replace fat in the fuel mixture,

(2) Then, and only if the carbs are greater than your total number of calories burnt per day (your energy expenditure), this surplus will be converted to fat.

So a person has to eat more carbs that all the calories being burnt by the body and do it for many days (to fill stores) before serious synthesis of new fatty acids happens (de novo lipogenesis). It seems that most people don’t get to this level of chronic excess carb intake, because we rarely see such high levels of DNL. But it can happen under those conditions.

Carb calories above what are burnt each day get stored first as glycogen. This usual glycogen pool is ~3,000 calories in the whole body. IF THEN you eat more carbs than your total amount of calories burnt per day (which is difficult to do), the glycogen pool can increase a bit (maybe double to 5-6,000 calories) but after that carbs above your total calories burnt per day may will be converted to fat.

So, first carbs are burnt or stored as glycogen; and only if there is no way to burn them (they exceed your total calories burnt per day) and there is no room in glycogen (the pool has expanded to it fullest amount), they are converted to fat. This scenario is hard to do and is not usual.

And Dr. Hellerstein concludes with this note:

Glycogen storage may account for some of the weight changes (lots of water is included when glycogen is present in a tissue).

But it also could be that the extra carbs are replacing fat in what your body burns. This is the main point I was making really – that carbohydrates can make you fatter without going through de novo lipogenesis

So thank you Dr. Hellerstein. That clarified a lot for me. And for myself, I will continue to consider the overall caloric intake of what I’m eating because, honestly, it seems to be the only way, in my case, to keep my lost weight off. For people who are still overweight, I think there is also an important message here about excess carbs being burnt for fuel before stored body fat is, which could inhibit getting rid of that excess body fat. That’s not to say carbs are the villain here. They are the healthy basis for whole food plant based living and controlling weight while enjoying satiety at the same time. Still, everything has its limits. As Dr. Hellerstein says, “There are no free calories. It’s just arithmetic.”