Dr.Jason Fung, a nephrologist and author of two previous books, “The Obesity Code” and “The Complete Guide to Fasting,” has now released a third, “The Longevity Solution,” which is the topic of this interview. This book was also co-written with James DiNicolantonio, Pharm. D, who also happens to be the co-author of my latest book, “Superfuel.”

The motivation for “The Longevity Solution” came from a discussion with DiNicolantonio. “He’d already talked about salt in his book, ‘The Salt Fix.’ In ‘Superfuel,’ he talked about good fats, bad fats and super fuel. We thought it would be great to tie everything together in terms of the real dietary determinants of longevity,” Fung says, adding:

“I spend a good section of the book talking about protein — the different types of protein, animal versus plant protein, for example, and how much protein [you need]. These are really important questions because there’s so much [information] out there, and you don’t know who to believe.”

From my review of the book, I think that is probably one of the most valuable pieces, because there’s so much confusion about protein. There’s good reason for this confusion, because it’s a complex topic. An important part of the equation is the mammalian target of rapamycin (mTOR), also known as the mechanistic target of rapamycin, a very important pathway responsible for controlling autophagy.

If you inhibit mTOR — which you can do by restricting protein — you activate autophagy, which is a good thing. However, I’ve personally made the mistake of not eating enough. While excess protein can activate mTOR, your protein needs do increase with age, as you need to counteract progressive loss of muscle mass. So, your age really needs to be taken into account as well.

Understanding the Role of mTOR

As noted by Fung, mTOR is basically a nutrient sensor. While insulin primarily senses your intake of carbohydrates, mTOR primarily senses protein. Different proteins will stimulate mTOR more than others. Fung explains:

“The reason is that mTOR senses the availability of protein and increases these growth pathways. If you’re trying to increase muscle, like bodybuilders will, for example, then this might be a very good thing. On the other hand, it impacts aging. One of the real interesting theories of aging is that there’s a sort of trade-off between the growth program and the longevity program.

That is, if you grow, it’s actually the same pathway as aging. Whether it’s good or bad depends on your age. When you’re young, you want to grow, so you activate all these growth pathways. But as you get older, if you keep revving that growth engine, it’s just going to burn out.

Just like your car engine, revving it is great if you want to go fast. But if, on the other hand, you want to keep that car for a long time, you don’t want to rev it that much. Things change as you go along.

During childhood and early adulthood, you want that growth program to go forward, but that growth program is intrinsically at odds with the longevity program. After a certain point, you may want to cut things back. That’s the understanding of mTOR; mTOR drives all this growth. But then as you get older, you wind up with diseases of too much growth …

There are all these chronic metabolic diseases where increasing the growth pathway, which is the same as the longevity-aging pathway, is not good. At some point, you want to slow it down. But as you get older, your body actually becomes resistant to some of these growth pathways.

Therefore, you actually need to take a little bit more. If you’re elderly and you’re at risk of falls, for example, then taking more protein might be a good thing. This is one of the reasons that protein is so hard to understand because everybody’s so different … You just have to look at your own situation.”

What Are Your Real Protein Needs?

All of that said, there are some general guidelines you can use to estimate your protein needs. Children, for example, generally need higher amounts of protein since they’re in growth mode.

Now, when calculating your protein needs, it’s important to make the calculation based on grams per kilograms (kg) of lean mass, not total body weight. The reason for this is because you do not need protein to maintain your fat mass. You need it to maintain your lean muscle mass. The following amounts can be used as a general guideline:


Children — 2 grams of protein per kg of lean body mass

Young adults — 0.8 grams of protein per kg of lean body mass

Adults — 0.6 to 0.8 grams of protein per kg of lean body mass

Bodybuilders — 1 to 1.2 grams of protein per kg of lean body mass

Endurance athletes — 1 to 1.5 grams of protein per kg of lean body mass

Seniors — 0.8 grams of protein per kg of lean body mass; possibly more if muscle wasting is a problem