In the Zero Carb community (us folks who eat only meat, eggs, cheese and butter) there has been much controversy over whether there is a need to limit the amount of protein we eat. I have followed many Zero Carb sites for the last 2 years that I have undertaken this way of eating myself. There seems to be ample evidence that a large number of people are able to reach their desired weight and be vigorous and healthy eating all the protein they want often eating 2-3 lbs of meat per day or in some cases more with no weight gain.
My own experience was that my weight loss on a program of unlimited protein consumption stalled after 4-5 months and after about 4 months of no progress I was able to restart my weight loss by initially limiting my protein. After much study the figure that seemed to be the most recommended by low carb doctors like Stephen Phinney and Eric Westman was to multiply the weight you wanted to weigh in kilograms by 1.5 and use the result as the maximum number of grams of protein you ate in a day. When I did this I was able to lose another 20 lbs before plateauing short of my goal again. The final piece to the puzzle for me was adding intermittent fasting which I won’t get into here but was the key that let me get to my ideal goal weight.
Many people have emailed me with the problem of stalled weight loss on Zero Carb and Low Carb diets and after deciding to limit protein have subsequently gone on to lose significantly more weight after doing so.
Here is my theory as to why some people who seem to have persistent resistance to insulin cannot tolerate high protein intake while other people can seemingly eat all the protein they want as long as they stay away from the carbs (and some lucky people can even eat all the carbs they want and stay at their ideal weight).
First I think there are many forms of insulin resistance. We understand a lot about the development of insulin resistance but certainly not everything. The common thing that happens in the 60-70% of all humans that will eventually develop first the Metabolic Syndrome and eventually Diabetes with the associated complications of a high risk of heart attack, stroke, kidney failure, loss of limbs, blindness and Alzheimer’s Disease among many of the complications of this progression if they eat a high carbohydrate diet is this – “Insulin Resistance” and insulin resistance inevitably leads to higher and higher blood insulin levels making it harder and harder to get the fat in fat cells out of the cells to be burned. However, 30-40% of people seem to be protected somehow and are able to eat a high carbohydrate diet without this progression. First this tells us that there is some genetic component to susceptibility to developing Insulin resistance – “We don’t all respond the same to carbs”. I personally think though I can’t find any controlled studies on this that we don’t all respond the same to protein.
First let me describe what I consider the theory that best explains the development of insulin resistance and is the one in favor with most of the prominent low carb doctors and researcher currently. On a high carbohydrate diet excess glucose gets converted to fat then stored initially in the peripheral fat however once these fat cells get full, fat cells that don’t usually store excess glucose as fat are forced to do so. These are the called the viceral fat cells or mesenteric fat cells and they are located in peritoneal cavity which includes the liver, the pancreas, the kidneys and the spleen.
When fat develops in the liver it causes the liver to become inflamed and damaged. This leads to Non-alcoholic Fatty Liver Disease (NAFLD) which is currently epidemic in Western Countries and felt to affect 30% of the adults in the US according to this study. NAFLD causes insulin resistance in liver cells per this study here’s a quote “NAFLD is considered the hepatic component of the metabolic syndrome and insulin resistance represents its pathophysiological hallmark.”. When the liver becomes resistant to insulin 2 really bad things happen. First, the liver stores glucose in the form of glycogen and when your blood sugar get low it dumps out glucose to bring your blood sugar level back up and when your blood sugar level goes back up this stimulates insulin release which should tell your liver “OK the sugar’s back up stop putting out sugar”. The problem is a liver resistant to insulin can’t hear insulin’s message and continues dumping out sugar until the insulin levels get really high and high insulin levels are a problem because insulin traps fat in fat cells where it can’t be burned leading to more viceral fat and even higher insulin levels.
The second huge problem with fatty liver is that the liver is responsible for transporting fat and Cholesterol around the body. Little “trucks” are built in the liver to carry fat and Cholesterol as they are not soluble in blood and must be transported by “lipoproteins” which you probably know as what you doctor calls the good Cholesterol (HDL) Cholesterol and the bad Cholesterol (LDL). This is not really true, you need both, and it’s healthy to have both kinds. The problem is that the LDL Cholesterol trucks are kind of “fragile” and are only meant to be used 24-48 hours then replaced. They can pick up and deliver Cholesterol and simple fat (triglycerides) all over the body to any cell that needs them. Normally they leave the liver with a big load of both (at that point the are actually called Very Low Density Lipoproteins (VLDL) and as they offload some of their cargo become the smaller LDL particles. What happens is that they are able to pick free triglycerides along the way and in carb eaters the triglycerides floating around in the blood are always higher than in low carbers. The liver is waiting for them to get fairly low in their load before gobbling them back up and reprocessing them as new trucks. If they keep picking up triglycerides out of the blood they don’t get small enough and also an inflamed fatty liver doesn’t seem to be as good at recognizing when they need to be taken out of the blood stream so the these fragile LDL trucks float around in the blood stream too long and wind up getting sugar molecules and other oxidizing particles stuck to them and become “Small Oxidized LDL particles” which are the ones that wind up in heart and brain arteries causing inflammation and plaque buildup eventually leading to heart attacks and strokes.
Meanwhile the fat deposited in the Pancreas is causing the beta cells which produce insulin to also become inflamed. Beta cells normally respond to eating carbs and protein by putting an initial “burst” of insulin called the first phase. This “insulin spike” is a signal to the liver to shut down sugar production. An inflamed pancreas is unable to put out this intial burst so sugar keeps getting dumped into the blood by the liver leading to eventually higher insulin levels to cover this output when the slow moving pancreas get up to speed. If there is enough inflammation from fatty pancreas for long enough beta cells can begin to die or just not be able to produce enough insulin to keep up with the high demands. This is the point when diabetics have to go on insulin which leads to even more fat deposition in the pancreas which just worsens the problem. Here are pictures of first a normal then a fatty pancreas.
Again, I can’t find any controlled studies on weight loss on low carb diets comparing people who did and did not control the amount protein they are and I doubt they exist so I am left with only anecdotal evidence. But my personal theory is that first some people are born with more insulin resistance than others. My best evidence for this is the 30-40% of people who don’t seem to become insulin resistant even on a high carb diet. And second I feel that in some people permanent damage can be done i the liver and pancreas that somehow renders them less tolerant of the insulin generated by protein consumption. I feel the group with either a high tendency to insulin resistance or residual damage to the endocrine system (liver, pancreas, spleen, kidnes etc.), a group into which I think that I fall can have problems with the lower levels of insulin release that proteins cause.
I have heard the argument that restricting protein will lead to malnutrition. I think there is good evidence to refute this claim at the level of protein I recommend. The World Health Organization recommends around 150 ml per kilogram of weight for breastfeeding infants. The Wikipedia give the protein content of human breast milk as 1.1 grams per ml. So babies are getting 1.65 grams of protein per kg during the most rapid and demanding time of human growth. I am very comfortable personally with 1.0-1.5 grams of protein per kilogram per day as I am not in a state of rapid growth.
There are arguments that a high protein intake over values as low as 0.6 grams of protein per kilogram per day can hasten aging, increasing the risk of cancer and lowering immune resistance through activation of the mTOR system. Dr. Ron Rosedale is one of the main proponents of this theory. You can hear his elegant presentation of this theory here. There is a lot of experimental data on animals to support it but no controlled studies on humans so it remains an unproven from my perspective. Still I find the evidence strong enough to err on the lower side of protein intake.
My personal position is that if you’re eating 2 lbs (32 oz) of meat a day you are getting about 224 grams of protein since meat averages about 7 grams of protein per ounce. If you weigh 150 lbs (68 kg) thats 3.2 grams of protein per kg per day. If you weigh 250 lbs (113 kg), 2 lbs of meat is still 2.0 grams of protein per kg per day. So if you’re eating more than 1.5 grams of protein per kg per day and you are not losing the weight you think you need to lose to get to a desirable weight and have given it 3-6 months of an honest trial, you might consider a 1-2 month trial of limiting protein to 1.5 grams per kg of desired weight per day. I know of at least 8 people including myself who have restarted weight loss on a Zero Carb diet by limiting protein to less than 1.5 grams of protein per day. And many prominent low carb doctors recommend protein restriction in this range for patients who are not losing enough weight on carb restriction only.
I do not advocate that all people limit protein. If unlimited protein is working for you, that’s great. I have never recommended “messing with success”.