In another life, I was a gym guy. Truth be told, I still am a gym bro, and I’ve come to terms with the fact that I’ll always be. As you probably know, I love CrossFit. I’ve been doing it for more than 5 years and it’s transformed my life physically, mentally, and spiritually
For me, CrossFit is so challenging, it requires a “no excuses” mentality, which forces me to stay very focused and systematic not only in the gym, but outside of the gym with what I eat, how much I sleep, and how stressed I allow myself to become.
When it comes to food in particular, athletes in general love to put protein at the center of the nutrition conversation, telling you that protein is the most important macronutrient, and that nothing else really matters in the long-run.
It feels like everyone attended the same “Protein is King” masterclass, signed up for the “Protein is Life” membership, and focuses their entire existence on the hunt for more protein when they’re not in the gym.
I often refer to my active friends as “Protein hunters” because that’s how they act, and I’m not afraid to tell them that the hunt for more protein may actually be HURTING their health in the long-term.
Short-Term and Long-Term Results are Not the Same
I talk a lot about the difference between short-term results and long-term results, and that he or she who focuses on the short-term only often ends up in a pickle down the road.
In the world of diabetes, short-term thinkers are all over social media, telling you to add fat and protein-rich foods like chicken, tuna, eggs (of any kind), olive oil, and almond butter to every meal because it will flatten your post-meal BG rise.
It’s true. It will. In the next few hours after a fat-rich and/or protein-rich meal, your BG will likely stay very well controlled, which makes you think that you’re doing something very right. But, what about the long-term effects? What happens when you’ve been eating this way for weeks or months on end? Do your blood sugars stay in control like they did in the short-term?
The answer is NO. People who eat more protein not only have higher blood glucose values, but they INCREASE their risk for many chronic diseases and increase their risk for premature death
It sounds drastic, I know. I’m not here to scare you. I’m here to tell you what the scientific literature actually says, because my guess is that you probably don’t read esoteric academic science in your spare time. At least I hope you don’t.
That’s what we’ll explore in today’s protein deep dive. We’re here to talk about both the short-term and LONG-term effects of “hunting” for protein at each meal, and what the scientific research says.
Protein Biochemistry in a Nutshell
Let’s get into the weeds of some Nutritional Biochemistry and start with the basics about what happens when you eat protein in food
And to do that, we’ll compare how protein is digested, absorbed, and utilized compared with carbohydrates. Carbohydrates are the simplest macronutrient, so it’s nice to use them as a comparison
When carbohydrates are broken down after you eat them, they are completely digested in your small intestine and then enter your blood as individual monosaccharides like glucose and fructose.
When glucose appears in your blood following a meal, your blood glucose increases, which in turn knocks on the door of your pancreatic beta cells to secrete insulin
Insulin is essentially a SIGNAL to cells to accept available glucose in your blood, which they then absorb and either burn for energy or store for later use.
The Protein Process
Now, with protein, it’s a bit different. When you eat food containing protein, the process of protein digestion is initiated by the gastric juices released by your stomach, which include hydrochloric acid and the enzyme pepsin.
In addition to this, muscular contractions known as peristalsis also play a role in digestion. The strong contractions of the stomach help to mix the partially digested protein into a more homogeneous mixture called chyme.
Your stomach plays an essential role in the digestion of protein because the internal environment is very acidic, with a pH between 1.5-3.5. This acidic environment causes proteins to denature, or unfold. This is similar to untangling a knot to straighten a piece of string, and this is the first step in digesting protein.
Denatured proteins lose their function because proteins are only active when folded in a VERY SPECIFIC MANNER. It's VERY important to note that the 3D structure of a protein is crucial to its proper functioning, so denaturation in the stomach not only begins the digestion process. It also destroys the protein's original function and prepares it to be converted into nutrients.
Pepsin then cuts large proteins into smaller protein fragments in preparation for more cutting in the small intestine.
Chyme then exits your stomach and enters the small intestine where it mixes with bile and a collection of digestive enzymes like chymotrypsin and trypsin, all of which continue to cut protein fragments into single AAs, double AA chains called dipeptides, or triple AA chains called tripeptides.
These amino acids are absorbed into your blood and are circulated to all tissues. Much like with glucose, insulin then signals cells to absorb those amino acids, and either turn them into new proteins via a process called protein synthesis if there’s a need OR convert them into other nitrogen-containing metabolites that are used as intermediary molecules in various biochemical pathways.
Amino Acids and More (Where It Gets Complex)
All cells have what is known as an intracellular amino acid pool which you can visualize as a swimming pool of amino acids that are undergoing a 24-7 recycling process. Amino acids (AAs) are added to the intracellular amino acid pool as proteins are being catabolized (or broken down).
AAs are also being taken out of the intracellular amino acid pool and added to new proteins via protein synthesis. So at all times, proteins are being catabolized (and added to the pool) and synthesized (or taken out of the pool), which means that this pool is in constant flux.
Now, I’ll be the first to tell you that amino acid metabolism is VERY complex, and takes YEARS to fully understand. So to keep things approachable and informative, this article will concentrate further on how eating protein affects your blood glucose and insulin dynamics.
Deadlifts and Diabetes | High Protein Diets and Insulin Resistance
A high-protein diet is commonly defined as a diet in which more than 20% of calories come from protein. So, first, let’s talk about how this affects your body composition.
The studies are clear that a high-protein diet leads to improved body composition (lower body weight and more skeletal muscle), especially in tandem with resistance exercise. This happens because, after resistance exercise, muscles are hungry for glucose, amino acids, and fatty acids to repair muscle tissue that’s experienced microtears.
Combined with the fact that exercise makes it much EASIER to maintain a caloric deficit, studies have shown that a high protein diet and resistance exercise have promise when it comes to specifically reversing obesity and promoting weight loss.
Now, diets like the Atkins diet, the carnivore diet, and the ever-popular ketogenic diet are all carbohydrate-restricted diets that often promote RAPID weight loss at the beginning, and that weight loss by itself improves glycemic control, independent of any other lifestyle changes.
That’s one of the reasons why people who eat a low-carb diet often see that their fasting BG goes down and their A1c goes down because…they’re losing weight!
And since weight loss directly increases insulin sensitivity, high-protein diets and low-carbohydrate diets both yield some immediate, positive results as long as the weight loss process is underway.
However, despite the fact that high-protein and lots of exercise may be a quick, effective weight-loss tool, the research shows that eating a high-protein diet can become problematic in the long term.
Deceptive Short-Term Results
Here’s why. At the start, high protein diets, if coupled with exercise, help reduce insulin resistance thanks to changes in your body composition – less body fat, and increased muscle mass. However, the research shows that over time high-protein diets by themselves do not have a meaningful effect on insulin sensitivity.
In fact, they increase insulin resistance! Wait what? Did you just say that a high protein intake increases insulin resistance? Yes, and I’ll repeat it once again
Eating a high-protein diet may suppress your blood glucose in the 3 hours following a meal and help promote weight loss in the short term, but high-protein diets cause delayed blood glucose rises starting about 3 hours after you eat a meal, and increase your baseline level of insulin resistance in the long-term.
And in the next section, we’ll explain how.
High-Protein Diets Worsen Glucose Metabolism
A recent study investigated the effect of losing 10% of body mass by eating a calorie-restricted diet containing either 0.8 g/kg or 1.2 g/kg of animal protein.
Even though the high-protein diet preserved muscle mass by 45%, it prevented weight-loss-induced improvements in muscle insulin signaling and insulin-stimulated glucose uptake.
Only subjects who ate the low-protein diet increased insulin sensitivity, and subjects who ate the high-protein diet did not.
In addition to modest changes in insulin signaling during weight loss, studies also demonstrate that diets high in protein cause late-onset postprandial hyperglycemia and late-onset postprandial hyperinsulinemia starting approximately 3 hours after a single meal in subjects with type 1 diabetes.
This is important because people with T1D are excellent test subjects because you can control 100% of their insulin requirements using injected insulin.In another eye-opening study, Wolpert et al. demonstrated that subjects with type 1 diabetes who were fed a high-fat dinner containing 60 grams of fat required significantly more insulin over the subsequent 18 hours than did subjects who were fed a low-fat dinner containing only 10 grams of fat. In addition, the high-fat dinner caused more hyperglycemia than the low-fat dinner despite increased insulin administration.
To study this, they performed a crossover design where subjects followed 2 separate tracks:
Track 1: They were fed a high-fat dinner and then monitored for the next 18 hours, followed by a low-fat dinner and monitored for another 18 hours
Track 2: They were fed a low-fat dinner and then monitored for the next 18 hours, followed by a high-fat dinner and monitored for another 18 hours
The summary of this study’s design can be seen in the next figure.
And you can see the results below:
Whether subjects consumed a low-fat, or high-fat diet, the addition of animal protein caused a long-term spike in blood glucose even after being administered more insulin.
A more clear correlation you won’t often find, and these results were supported by Paterson et. al in their extensive study on dietary protein in glycemic control.
And when you understand the mechanism behind protein-induced insulin resistance (which we’ll explore now), this makes a lot of sense!
The Untold Mechanism of Protein-Induced Insulin Resistance
There are actually TWO predominant mechanisms that explain why high protein intake causes postprandial hyperglycemia (high blood sugar after a meal).
The first is that researchers have discovered that a high intake of animal protein stimulates glucagon production by pancreatic alpha cells. These are the cells located next to the beta cells, all contained within the Islet of Langerhans.
What does glucagon do? It promotes hepatic gluconeogenesis (the synthesis of new glucose) and increases hepatic glucose production. In other words, it causes your liver to manufacture more glucose internally and it causes your liver to secrete more glucose into the blood
In subjects without diabetes, glucagon stimulation occurs simultaneously with insulin release and the two pancreatic hormones counteract one another. Glucagon acts to increase blood glucose while insulin acts to decrease blood glucose by increasing glucose disposal.
The net effect is a minimal glycemic impact, which is exactly why non-diabetic people don’t experience any changes in their blood glucose profile. Think of this as a tug-of-war between glucagon and insulin, both of which are increased, leading to a net NEUTRAL response and no significant BG rise.
But in patients living with type 1 diabetes, protein-induced glucagon secretion leads to a net rise in how much glucose is produced by the liver, increasing your blood glucose and thus increasing your insulin requirements.You can see this below, in two charts from Winiger et al. from their study on the subject.
This is an even stronger rise than from fat, which is one of the main culprits of diabetes! Important to learn from this.
The second reason protein causes insulin resistance is slightly different. Researchers have estimated that approximately 20-40% of the protein you eat is DIRECTLY converted into glucose in the first 8 hours following a meal via an AA-to-glucose conversion
These AAs are known as GLUCOGENIC amino acids, and their uptake is increased in the liver when you eat a high-protein diet. This increases the conversion of these amino acids to glucose, thereby increasing liver glucose production and raising blood glucose compared to similar meals in a low-protein diet.
So to recap, the 2 mechanisms that lead to increased BG following a high-protein meal are:
- Increased glucagon production and
- Direct conversion of amino acids to glucose in the liver
So in summary, if you’re trying to keep your BG low after a meal, then eating more protein doesn’t always get the job done for these 2 reasons. But there are even more reasons to take note of this interaction.
Double Day! | Fat and Protein’s Effects are Additive
In addition to the negative impact of increased protein intake, a wide range of scientific evidence demonstrates that increased dietary fat promotes the development of insulin resistance in both the liver and muscle.The mechanism of fatty-acid-induced insulin resistance results in decreased glucose uptake in the liver and muscle. We talked about this in the Mastering Diabetes Book in detail. It’s a complicated chemical process, but we’ve reduced it down to the basics in this image.
The Additive Effect
Make no mistake about it – IR develops from an increased fatty acid flux in the muscle and liver, which impacts these insulin-responsive tissues and results in a significant reduction in insulin action and insulin signaling in both tissues.
However, as we mentioned before these effects stack on top of each other.
Lipid- and protein-induced insulin resistance is particularly problematic in patients living with type 1 diabetes because the inclusion of both fat and protein worsens postprandial glycemic control within hours of a single meal and can significantly complicate blood glucose control.
How Much Protein is Correct?
At this point, many people are often saying to us – “okay okay, I get it. So how much protein should I eat?”
To keep things as simple as possible, we’ve created some general recommendations that you can easily follow when eating a 100% plant-based diet. And yes, you can meet and exceed your protein requirements when eating a plant-based diet. We’ll do a deep dive into that specific topic in a future video.
We like to think of protein intake in terms of grams per protein ideal body weight, rather than a percentage of calories. The reason is simple – percentages fluctuate and can cause a lot of confusion, but grams are hard numbers that don’t change. Keep it simple.
Step 1: Calculate your ideal body weight in pounds
Step 2: Divide that number by 2.2 to convert it into kilograms
Step 3: Determine your average activity level, and classify that as low, medium, or high.
Low = I’m relatively sedentary and don’t move my body unless I have to (0-1 hour per week)
Medium = I move my body regularly and average about 1-3 hours per week
High = I move my body regularly and average about 3-10 hours per week OR
High = I move my body regularly and am specifically trying to gain muscle via hypertrophic gym sessions (you know what that means if you do it)
Low = Multiply your ideal body weight in kilograms by 0.8. That’s the number of grams of protein you could aim to eat per day.
Medium = Multiply your ideal body weight in kilograms by 1.2. That’s the number of grams of protein you could aim to eat per day.
High = Multiply your ideal body weight in kilograms by 1.6. That’s the number of grams of protein you could aim to eat per day.
My ideal body weight is: 165 pounds
My activity is: High (7-10 hours of intense exercise per week)
So if you do that equation, my ideal amount of protein is: 165 pounds / 2.2 = 75 kg * 1.4-1.6 = 105-120 grams of protein per day.
Regardless of your level of activity, aim to keep your protein intake at any given meal less than 30 grams, otherwise, you may experience an unwanted BG rise after the meal. Don’t say that you haven't been warned!
And if you’re curious about how to measure your actual protein intake, download Cronometer from the app store and begin using it as soon as possible. Just list what you eat and how much you eat, and Cronometer will do all the calculations behind the scenes to tell you exactly what you’re eating so that there’s no guessing.
Final Thoughts on Protein
There’s a lot of science in this article and even more in the companion video, and we don’t want you to get overwhelmed with numbers that are impossible to remember. So all that you have to remember is this:
Protein is a necessary component of your diet, but more is not always better, especially when it comes to regulating your blood glucose control today and many months into the future
If you’re interested in weight loss:
When it comes to weight loss, yes, increasing your protein intake can temporarily help you lose weight, and that in turn can improve your BG values and lower your A1c. When you lose weight, your insulin sensitivity should go up big time, and that’s a good thing.
But when you eat a protein-rich diet and lose weight, your insulin sensitivity goes up, but not nearly as much as it would if you were eating a low-protein diet. So in effect, you’re getting some improvements, but not as much as you could be getting
If you’re living with any form of diabetes, then:
Even though your experience may be that adding protein to a meal suppresses your BG for a few hours after the meal, doing this repeatedly will increase your level of baseline insulin resistance, which will increase your fasting BG and A1c over months and years.
In other words, eating a high protein diet may suppress your blood glucose in the 3 hours following a meal and help promote weight loss in the short-term, but high protein diets cause delayed blood glucose rises starting about 3 hours after you eat a meal, and increase your baseline level of insulin resistance in the long-term.
Also, it’s important to remember that the effects of fat and protein are additive – when both 30 grams of fat and 40 grams of protein are added to a meal containing 30 grams of carbohydrate, postprandial glycemia can be increased by as much as 100 ng/mL, which is a big deal.
To calculate your ideal protein intake:
Step 1: Calculate your IDEAL body weight in pounds
Step 2: Divide that number by 2.2 to convert it into kilograms
Step 3: Determine your AVERAGE activity level, and classify that as LOW, MEDIUM, or HIGH
LOW = Multiply your ideal body weight in kilograms by 0.8. That’s the number of grams of protein you could aim to eat per day.
MEDIUM = Multiply your ideal body weight in kilograms by 1.2. That’s the number of grams of protein you could aim to eat per day.
HIGH = Multiply your ideal body weight in kilograms by 1.6. That’s the number of grams of protein you could aim to eat per day
Now, before we go: these are just recommendations, though they are recommendations backed by dozens of peer-reviewed studies. As with anything in your diet, you’ll have to experiment to find the correct protein load for yourself or with your dietitian/nutritionist.
But with this information, you’ve got the tools to make educated and informed decisions.
If you’d like to learn more about this topic, you can watch the full companion video here. And if you’d like to take the next step and start transforming your diabetes health today, you can book a free, no-obligation discovery call by clicking here and visiting www.masteringdiabetes.org/start.