Losing weight requires expending more energy (calories) than your body needs to support its normal functions and carry out daily activities, including exercise.
This can be achieved by increasing the number of calories you expend through exercise or decreasing the number of calories you consume from food and drinks, but ideally both. However, doing these things is easier said than done, especially for people whose biological drive to eat is difficult to manage in today's obesogenic environment.
Fortunately, glucagon-like peptide-1 (GLP-1) agonists — initially approved to improve metabolic control in patients with diabetes — have demonstrated strong weight loss results in people even without diabetes, leading to their increased popularity for weight loss. They promote weight loss primarily by slowing gastric emptying, increasing satiety, and reducing appetite (1).
Despite their efficacy, they can cause adverse effects, a major one being muscle loss, which is counteractive to both metabolic health and weight loss success. The best way to combat this muscle loss is by strength training regularly but protein has a key role too.
This article breaks down the benefits of a high-protein diet for weight loss with a focus on those using GLP-1 agonists.
Weight Loss or Muscle Loss?
When people attempt to lose weight, pounds loss is the primary metric, but what those pounds consist of is more important.
Most assume that much of what they lose comes from fat but there are also losses in lean body mass — including muscle — often exceeding 35% of total weight loss (2).
For people taking GLP-1s like semaglutide (Ozempic), dulaglutide (Trulicity), liraglutide (Victoza), and the like, some trials have demonstrated reductions in lean mass ranging between 40% and 60% as a proportion of total weight loss (3).
Now, this doesn't mean that 40% to 60% of muscle is lost since lean body mass also encompasses organs, bones, fluids, and water in fat tissue, but the loss in muscle can still be significant.
Consequently, the increased loss in lean body mass decreases metabolic rate to a greater extent than if more fat mass were lost, making it more difficult to lose and maintain weight.
To this point, the number of calories you burn at rest decreases three times more for every kilogram (2.2 pounds) of muscle lost compared with the same amount of fat (3).
Declines in muscle mass can also disrupt metabolic health since skeletal muscle is responsible for most glucose uptake from the blood (4).
A person's starting weight, diet, and activity level largely determine whether more weight is lost from muscle or fat.
From a nutritional standpoint, the degree of caloric restriction strongly influences lean body mass, but one of the most effective ways to mitigate muscle loss and prioritize fat loss is by increasing protein intake.
In addition to sparing muscle loss, upping your protein also supports weight loss by increasing satiety or feelings of fullness, and because of its thermic effect — protein requires the most energy to digest and process, followed by carbs and fats.
How Much Protein is Optimal?
Protein preserves muscle loss during caloric restriction by suppressing muscle protein breakdown.
The current recommended dietary allowance (RDA) of protein for adults is 0.8 grams per kilogram (0.36 grams per pound) of body weight per day, equating to 55 grams for a 150-pound person.
However, the RDA is the minimum amount necessary to prevent a protein deficiency — it says nothing about what is optimal for health or performance.
Instead, most data suggests consuming around 1.5 to two times the RDA of protein to support lean body mass retention while dieting in otherwise healthy young, middle-aged, and older adults. This range equates to about 83 to 110 grams of protein per day for the same 150-pound person (5).
Athletes — depending on the severity of the caloric deficit and type of training type and intensity — should aim for the higher end of this range, with some data suggesting up to three times the RDA to promote muscle mass retention and fat loss (6).
Recall that the degree of caloric restriction also strongly influences lean body mass retention — the greater the restriction, the more potential for lean body mass loss.
To better preserve lean body mass in combination with a high protein diet, a moderate caloric restriction of 300 to 500 per day is ideal. This deficit can be achieved for most people by decreasing portion sizes — but not of proteins (7).
Tips to Increase Your Protein Intake
Increasing your protein intake while trying to cut calories can be overwhelming.
A good place to start is to look at the current lean proteins you already consume or like and double the portion.
Lean proteins are those that are low in fat and calories but high in protein.
Lean proteins include foods from both animals and plants.
Animal-based lean proteins:
- Chicken breast (skinless)
- Turkey breast (skinless)
- Fish (such as cod, tilapia, and haddock)
- Shellfish (like shrimp, crab, and lobster)
- Egg whites
- Lean cuts of beef (like sirloin, tenderloin, and eye of round)
- Pork tenderloin
- Low-fat dairy products (such as Greek yogurt, cottage cheese, and milk)
Plant-based lean proteins:
- Tofu
- Tempeh
- Edamame
- Lentils
- Chickpeas
- Black beans
- Quinoa
- Peas
Along with these foods, protein supplements are an efficient — especially in terms of calories and consumption — and cost-effective way to meet your protein goals.
Aside from the traditional protein shake, you can add protein to smoothies with low-calorie ingredients or mix it in soups and yogurt.
You can also stir into oatmeal using PEScience's Protein4Oats or make protein pancakes using their Protein Pancake and Waffle Mix.
A high-quality whey and casein protein blend like Select Protein can suit everyone's protein needs — plus it's available in more than 10 delicious flavors.
The Bottom Line
Most people assume that the weight they lose comes solely from fat. but up to 35% of it can actually be lean body tissue like muscle mass.
While effective for promoting weight loss, GLP-1 agonists can increase the proportion of lean body mass loss to as high as 60%.
Fortunately, increasing protein is one of the best ways to mitigate muscle loss and ensure that most of the weight you lose comes from fat.
Most research suggests consuming 1.2 to 1.5 grams of protein per kilogram (0.55 to 0.7 grams per pound) per day, with athletes potentially requiring a higher amount.
Opt for lean sources of protein like chicken breast, low-fat dairy products, and lean cuts of beef and pork. Peas, quinoa, and chickpeas are high-quality plant-based proteins.
Still, meeting your protein needs from these foods alone can be difficult — and sometimes costly — to achieve, making protein powders a convenient and cost-effective way to supplement your intake.
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