Why Protein Reigns King When it Comes to Weight Loss
Protein is considered to be the darling of macronutrients when it comes to the realm of nutrition and weight-loss. While I’m sure you are familiar with low-carb diets and low-fat diets, rarely do you see a diet that is intentionally labeled as low-protein — and there is a good reason for that.
Protein serves as the building blocks for virtually all cells and is the architecture of muscles, bones, skin, hair, organs and various tissues. Because our bodies are always in a state of cell turnover, we require an adequate supply of protein for cellular repair and growth. Protein also powers thousands of chemical reactions in the body, helps regulate hormone function, and distributes oxygen throughout the body.
There are multiple reasons why we need protein in our diet, but when it comes to weight-loss it is especially important. In the following article, I explain what happens to the body in a catabolic state (i.e. weight loss), the role protein plays in the weight-loss equation, and practical tips for incorporating protein into your diet.
What Weight-Loss Does For Your Metabolism
The first thing to keep in mind when it comes to weight-loss is that the weight we lose is not all body fat. Sorry to break it to you, but inevitably we will lose a combination of fat mass and lean body mass under a calorie deficit. Research suggests that overweight and obese individuals may lose 20–30% lean body mass on a calorie-reduced diet, whereas normal weight individuals may lose up to 35% lean body mass. Obviously, there are multiple factors that influence how much lean body mass is lost and/or preserved during weight loss and dietary protein heavily impacts this.
A main goal in weight-loss should always be to lose primarily body fat while sparing as much lean body mass/muscle mass as possible. This is because muscle mass plays a vital role in powering daily movement, reducing risk of injury, preventing fatigue, and maintaining a higher resting metabolic rate (RMR) — a key factor in weight-loss.
Your RMR accounts for the majority (60–75%) of your total daily energy expenditure. It represents the energy (i.e. calories) that is expended to keep your body alive at rest (e.g., heart beating, blood circulating, organs functioning like they need to).
Ultimately, weight loss triggers a reduction in RMR because a lighter body requires less energy to function. However, if you can preserve as much muscle mass as possible while losing body fat, you can keep your metabolism elevated which makes achieving an energy deficit that much easier.
Protein’s Role in Preserving Lean Muscle Mass
The amount of protein you consume during weight-loss directly impacts the proportion of muscle mass either lost or preserved. A recent meta analysis looked at 24 clinical trials that compared higher protein diets containing between 27–35% of daily energy as protein (1.07–1.60 g protein per kg body weight) with the lower protein diets containing 16–21% of daily energy as protein (0.55–0.88 g protein per kg body weight). For reference, all diets were within the Acceptable Macronutrient Dietary Range for protein (i.e., 10–35% of calories) issued by the Food & Nutrition Board.
Despite both lower protein and higher protein diets all having a similar caloric content, participants on the higher protein diets lost more total weight, body fat, and preserved more lean muscle mass (1).
The RDA for Protein is Not Sufficient for Weight-Loss
The lower protein diets contained closer to the Recommended Dietary Allowance (RDA) for protein which is set at 0.8 grams per kilogram of body weight or 0.36 grams per pound. The RDA is the average daily level of intake sufficient to meet the nutrient requirements of nearly all (97–98) healthy people (2). However, the RDA does not apply to catabolic situations that increase protein needs, such as weight-loss. Consequently, the participants on the higher protein diets (consuming up double the RDA) not only lost more weight but preserved more lean muscle.
How Much Protein To Consume During Weight-Loss?
Similarly, another meta-analysis including short-term weight-loss and long-term weight management studies demonstrated that consuming 1.2–1.6 grams of protein per kilogram is recommended for improving body composition during weight loss. This translates to ∼89–119 g protein per day for women or ~104–138 g protein per day for men (3).
Another way to look at this, is to multiply your weight in pounds by 0.5–0.7 grams (this is equal to 1.2–1.6 g per kg recommended in weight-loss studies). For example, a 180 pound individual attempting to lose weight would need to consume a minimum of 90 grams of protein per day (0.5 g x 180 = 90 grams).
If 90 grams of protein seems like a lot, remember that protein from all food sources count toward your daily protein intake. This includes protein from dairy, beans, grains, nuts, seeds, vegetables, in addition to meat.
Note: consumingly a higher protein diet during weight-loss is not a license to consume all the ribeyes and bacon you want, sorry. When choosing animal protein ensure you are choosing minimally processed, lean cuts of meat to avoid consuming excess saturated fat, sodium, and sugar which could negate its health benefits.
What approximately 90 grams of protein might include:
- Breakfast — 2 eggs (12 g) + 2 slices of Ezekiel bread (8 g)
- Lunch — 3 oz of chicken breast (27 g) + 1 cup quinoa (8 g)
- Snack — 6 oz of Greek yogurt (17 g) +1 oz almonds (6 g)
- Dinner — 1 Cup lentil soup (18 g)
The Benefit of Distributing Your Protein Intake
Another thing to keep in mind is how much protein you consume at one time. Typically, Americans eat an adequate amount of protein at lunch and dinner but breakfast is either lacking in protein (e.g., cereal, toast, granola bars) or is non-existent.
A 2020 study attempted to replicate this common dietary pattern. In a 12-week trial researchers compared a skewed versus equally distributed protein intake on muscle mass changes during a resistance training program.
One group of men were assigned to a skewed protein diet in which protein intake was the lowest at breakfast, more moderate at lunch, and the highest at dinner. Whereas a second group of men were assigned to a meal pattern in which protein intake was evenly distributed across meals. Both groups participated in the same resistance training program three times per week.
While both groups of men consumed the same total amount of protein per day, the group of men who shifted more protein to earlier in the day (i.e., breakfast) which provided an equal distribution of protein across all three meals, experienced greater muscle gains (4).
The main reasoning why distributing your protein equally across meals may be advantageous is that the body can handle only so much protein at one time.
Researchers hypothesize that “Unlike fat or carbohydrate, the human body has limited capacity to transiently store “excess” dietary protein from a single meal to acutely stimulate muscle protein anabolism at a later time (5).”
Quantities of 25–30 grams of protein per meal are generally considered beneficial for weight management and appetite control (6).
Proteins Impact on Hunger/Satiety
One of the worst parts about being in an energy deficit is feeling chronically hungry. Consuming an adequate amount of protein while losing weight may help curb hunger.
A study in Obesity, revealed that when 27 overweight/obese men were assigned to an energy restricted diet either higher in protein (25% of calories) or lower in protein (14% of calories), the men on the higher protein diet experienced reduced hunger, desire to eat, and preoccupation with thoughts about food (7).
Countless studies including this one have demonstrated that protein is the most satiating macronutrient, followed by carbohydrate, with fat being the least satiating (8)
Why We Feel Full After Eating Protein & Thermogenesis
Protein-induced satiety is believed to happen for a few reasons. Upon consumption it increases satiety-related hormones (GIP, GLP-1), decreases hunger hormones (ghrelin) and increases thermogenesis.
Thermogenesis, a component of total daily energy expenditure, is essentially the energy expended to digest and metabolize nutrients. Did you know it takes approximately 16% more energy to break down protein into its individual amino acids than to break down fat or carbohydrates into their constituents — fatty acids and glucose (9)?
While 16% might not seem like a lot, over time the additional calories needed to process protein can help one achieve an energy deficit.Thermogenesis is also believed to play a significant role in eliciting feelings of fullness.
Other Considerations for Preserving Muscle Mass
Start with a Moderate Calorie Reduction
When it comes to losing weight, aim for reducing calories no more than 40% of your baseline calorie intake. Think of your baseline calorie intake as the number of calories you’d typically consume when not dieting.
According to a study last year, “the protective effect of higher-protein diets on muscle and whole-body protein homeostasis is compromised as the severity of energy deficit increases beyond 40% of daily energy needs, as a greater proportion of dietary amino acids are oxidized for energy production, thereby minimizing amino acid availability to support protein balance (10 ).”
In other words, be patient when it comes to weight loss. Ultimately, a slower rate of weight-loss will lead to better body composition results not to mention feeling less deprived by eating fewer calories. Personally, I recommend no more than a 25% energy deficit when losing weight. If you typically consume 2000 calories per day (under normal conditions), reduce your calories by 25% or 500 fewer calories per day to promote weight-loss.
Pair a Higher Protein Intake with Resistance Training
Another way to spare muscle mass loss during weight-loss is to pair your higher protein diet with resistance training. Several studies have shown that resistance training exercises (i.e., working against a weight or force) counteracts muscle mass loss during weight-loss while also improving muscle strength (11).
A study that included 59 men and women with type II diabetes evaluated weight-loss and body composition changes on a higher protein (33% protein) versus lower protein diet (19% protein) — both with or without strength training. The group assigned to the higher protein diet with strength training achieved greater weight loss and favorable body composition changes than the diet alone groups or the lower protein diet coupled with strength training (12).
The Physical Activity Guidelines for American recommend resistance training 2–3 times per week to the point at which it is difficult to complete another repetition. Examples of resistance training include using free-weights (dumbbells or barbells) weight machines, resistance bands, or using your own body weight.
Practical Applications for Dietary Protein Relative to Weight-Loss
Eating nearly double the RDA for dietary protein during weight-loss is beneficial for preserving muscle mass (thereby increasing your metabolic rate) and controlling appetite — two important factors in a successful weight loss program.
If you are attempting to lose weight consider implementing the following strategies:
- Increase total dietary protein to 0.5 -0.7 grams per pound of body weight
- Distribute your dietary protein evenly throughout your meals
- Incorporate strength training into your weight-loss plan
- Reduce calories a moderate amount (25% reduction) to optimize body composition changes during weight-loss
- Choose protein sources that are nutrient-dense but also low in added sugars, sodium, and saturated fat to promote overall health and wellness
Before beginning any weight-loss program, consult with your doctor or a dietitian who specializes in weight-management to determine what dietary approach will work best for you.
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