Can you really use plant protein for weight loss?
According to many of the leading authorities on plant-based, vegan and raw food nutrition, protein is just a given on their prescribed diets – something you never have to think about because it’s impossible to not get enough if you stick to the whole foods they endorse.
If pressed, they’ll often cite the fact that babies go through their greatest period of growth consuming only breast milk, which derives just 6% of its calories from protein. But as I’ve mentioned previously, this argument doesn’t hold up to scrutiny.
In my last article I pointed out that a lot of protein ideologies in the plant-based movement are a decade or more behind the latest science. Not only does current research support extra protein leading to better athletic performance, greater bone density and strength, more muscle mass in old age, and improved antioxidant function, but, as I’m going to focus on in this article, it also seems to makes weight loss go a lot smoother.
The Skinny On Calories And Weight Loss
If you want to lose weight, you must consume fewer calories – either unconsciously because your diet makes you full and you eat less, or consciously by tracking calories, engaging in intermittent fasting, etc. Decades of metabolic ward studies – where people are locked up and all their caloric intake and exercise is monitored – have yet to find a significant exception to this rule.
There are some variables in metabolic rate, non-exercise induced thermogenesis, and a few other elements of metabolic function which can confuse people, but basically this has been a universal fining of weight loss research.
But the weight loss created by the same calorie deficit can actually vary greatly between different people. Two overweight people of the exact same size, height, and body fat percentage can each lose 30 pounds using the same calorie deficit, but one will lose significantly more fat and the other more muscle.
On average, studies have generally found that 20-30% of the body weight lost during dieting is from lean body mass (including muscle mass), but the exact this is not a universal finding, as we’ll be exploring today.
At the risk of being obvious, losing more lean mass than you absolutely have to during weight loss is a bad idea for three reasons:
- Aesthetics: Loss of muscle makes many people look skinny fat instead of lean after they’ve lost weight, and you may be able to lose less total weight to reach your aesthetic goal if more of the weight you do lose is body fat instead of muscle.
- Health: The more lean mass you lose, the greater the decline in your metabolic state, and the more open you are to sarcopenia and fractures in old age.
- Practical Strength: Despite modern man living in a labor-saving-device-filled world, we still need strength. That couch won’t lift itself, and if you ever need to climb or descend in an emergency, having lost pounds of muscle during your recent weight loss won’t do you any favors.
What Research Tells Us About Protein For Weight Loss
There are two well-established paths to preserving your muscle during weight loss, and both work by stimulating muscle protein synthesis (MPS). These are:
Let’s start off with a study of people put on a diet that restricted weight-maintenance caloric needs by 500 calories a day for a year2. This is fairly representative of the moderate weight loss goals many people have. In one group, participants were given the standard RDA-suggested protein intake of 0.8 g/kg/day, or 15% of calories from protein, while the other got 1.6 g/kg/day, or 30 % of calories from protein.
Unsurprisingly, each group, regardless of gender, lost a similar amount of weight. The high protein group lost 10.7 % of their bodyweight on average, while the low protein group lost an average of 10.1%.
But here’s where things get interesting.
How much of the weight loss was from muscle? Men in the low protein group lost 5.9 kg (12.98 lbs) from muscle on average, while the high protein group only lost 2 kg (4.4 lbs) from muscle.
That is an incredible difference that’s indicative of large disparity in body appearance and metabolic function. The members of both groups would have looked dramatically different, despite the same amount of total weight loss. A similar contrast played out with the women, although the differences were smaller.
But this is hardly the only study that’s found this strong connection between muscle retention and protein intake.
This one 3 put obese women on a diet that was 750 calories/day lower than required to maintain their weight, with half getting 30% of their calories from protein, and the other group receiving 18% of their calories from protein.
At the end of three months, both had lost a similar amount of bodyweight, but the higher protein group has lost an average of 1.5 kg (3.3lbs) of muscle, compared to 2.8 kg (6.16lbs) for the low protein group.
A study 4 comparing a group consuming 15% of its calories from protein and another consuming 30% of its calories from protein found the low protein group lost more weight (11.4 kg vs 8.4 kg), which sounds amazing.
But when you actually examining the nature of that weight loss, you see that a shocking 37% of it was muscle in the low protein group, while the high protein group’s weight loss was only 17.3% muscle. So despite losing less weight, the high protein group came out ahead.
There are literally dozens of studies released in the last 15 years which have found variations of this theme: consuming the RDA for protein (0.8 g/kg) or lower during weight loss will lead to unnecessary excessive loss of muscle mass. Here are three more for those who want to examine the science a bit more 5 6.
Strength Training vs Protein For Weight Loss
As I’ve discussed before, there’s a good deal of research indicating that strength training while you’re running a calorie deficit will help preserve your muscle mass.
But could protein or strength training be enough to do the job in isolation? Maybe you can just pick one or the other?
Unfortunately, the available research that we have indicates that they both work together synergistically to preserve muscle mass, so you’ll need both if you want to minimize muscle loss.
For instance, this study 7 divided the non-athlete participants into four weight loss groups. There was a high carb diet (0.8 g/kg protein) group, a high carb diet group that also did strength training two days a week and walked 5 days a week, a higher protein group (1.6 g/kg protein), and a fourth group on the same higher protein diet that also did the strength training and walking.
The researchers found that exercise protected muscle from being broken down regardless of the diet, but only the group that ate the higher protein diet and exercised saw no statistically significant muscle loss (−0.9% of their starting lean mass). The high carb group that didn’t exercise lost the most muscle (-5.4% of their starting lean mass). Of course, the high protein + exercise group also lost the most body fat, as displayed in the chart above.
Protein For Weight Loss And Muscle Retention In Serious Athletes
Everyone wants to race to lose weight. They want to be thin now, so they do questionable things like run huge calorie deficits that are hard to maintain and which tax their bodies heavily.
These are the kind of “cuts,” that bodybuilders do when getting ready for competition.
But can high-protein diets preserve our lean mass in even these extreme conditions?
In this study8, researchers recruited 22 athletes who did strength training an average if 4.9 times a week. They were put on a diet that restricted them to 60% of the amount of calories they needed to maintain their weight – a really high deficit that’s kind of crazy, and one I would not advise. This went on for two weeks.
Half were given food containing 15% of its calories protein (1.0 g/kg), which is already more than the RDA. The other half were given food getting 35% of its calories from protein (2.3 g/kg). 2.3 g/kg is a ton of protein to be eating, just to be clear.
The low protein diet group lost more total weight, but a large chunk of it was composed of muscle and other lean mass (-1.6 kg). The high protein group only lost 0.3 kg. Both groups lost similar amounts of fat.
While I wouldn’t suggest such a steep calorie reduction, it’s interesting to see that participants were able to preserve most of their muscle in the face of it if they consumed enough protein.
But it’s also worth noting that the 1.0 g/kg target also prevented far more muscle loss than you’d expect given the size of the deficit.
Protein For Weight Loss: The Take Home Message
Given what we’ve seen here, it makes a lot of sense for anyone who wants to lose body fat but preserve lean mass to increase their protein intake to well above the RDA while engaging in vigorous strength training multiple times a week.
How much protein should you consume? We don’t know what the optimal amount is; we just know that it’s more than the RDA. It’s very likely that the answer depends on how big of a calorie deficit you’re running, your genetics and hormonal state, and how vigorous and frequent your resistance training is.
However, as I mentioned in my previous article on protein for general health and athletics, 1.2 g/kg seems like the minimum target a person should shoot for in general life, so you probably don’t want to go below this target during weight loss. This is a target that can be hit eating only whole vegan foods if you’re careful about choosing higher-protein options.
Noakes, M. Et al. Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women. Am J Clin Nutr. 2005 Jun;81(6):1298-306. Link. [/footnote [Footnote] Clifton, PM. Et al. High protein diets decrease total and abdominal fat and improve CVD risk profile in overweight and obese men and women with elevated triacylglycerol. Nutr Metab Cardiovasc Dis. 2009 Oct;19(8):548-54. Link.↩