Although low-carbohydrate and low-fat diets are well-known methods that help with weight loss, high-protein diets can also be effective. However, high-protein diets involve more than eating just protein. Rather than directing you to consume only meat, high-protein diets simply restructure the amounts of macronutrients you consume. This way, you're consuming more protein than average, but are still incorporating carbohydrates and fats into your diet.
Eating just protein would probably make you lose fat, but this wouldn’t be healthy. Increasing your protein consumption while still consuming some carbohydrates and fats is a much healthier way for you to lose weight.
Eating Just Protein
There are many diets that involve eating only protein. Some of them, like the carnivore diet, recommend consuming protein only from animal sources. According to their supporters, these diets may help with weight loss and the management of certain health problems, like joint pain or tendon injuries.
Unfortunately, there aren't any scientific studies to back up these statements. Since nutritionists typically consider fad diets like this to be unhealthy, it is unlikely that there will be. All-protein diets like the carnivore diet are considered to be bad for you because they recommend primarily consuming foods like steak and pork loin, which tend to be high in saturated fat.
Over time, diets filled with saturated fat can cause increases in your cholesterol and triglyceride levels. This, in turn, increases your risk of heart problems. Diets rich in meat products may also increase your risk for certain types of cancer, since excessive consumption of red meat has been linked to colorectal, pancreatic and prostate cancer.
Of course, protein-rich diets also exist in other forms. No carb and low-carb diets, such as the Dukan diet, also advocate the consumption of protein. However, this diet recommends the consumption of pure protein — not fatty proteins — and only for a limited period of time.
Background of Protein-Rich Diets
Throughout history, people have consumed a variety of protein-rich diets. Given the history that humans have as hunter-gatherers, many people believe that the human body is better suited to high-protein, low-carb diets. Many current high-protein diets, including fad diets like the carnivore diet, are consequently based around paleolithic or Inuit-type diets.
Although paleolithic and Inuit diets may be similar in principle, as they both omit many carbohydrates, these diets still allow people to consume plant-based foods. This means that protein can come from foods other than meat and that meat sources are varied.
High-Protein Paleo and Inuit Diets
In the paleo diet, fruits and vegetables can be consumed freely. Grains, dairy and legumes are the main types of foods that are restricted. Unlike the carnivore diet, however, the paleo diet has well-established health benefits. People who consume low-carb, high-protein diets like the Paleo diet have shown improved blood pressure and glucose tolerance and lowered cholesterol and triglyceride levels in as few as 10 days.
The Inuit people have also traditionally consumed high-protein, low-carb diets. However, Inuit-type diets have less well-established benefits. In fact, the Inuit are also known to have increased likelihood of brain hemorrhages, though this has not been definitively linked to their dietary choices.
Unlike many low-carb, high-protein diets in Western society, Inuit-type diets obtain most of their protein from marine sources. People who follow these types of diets not only consume fish and shellfish, but also the predators of these creatures: whales and seals. Inuit-type diets are consequently low in saturated fat and rich in omega fatty acids.
While omega fatty acids are good for your health and much better for you than saturated fat, the Inuit people have genetically and physiologically adapted to consuming a diet that's substantially richer in polyunsaturated fatty acids than the diet of the average person. Additionally, a modern-day Inuit-type diet might be high in mercury. Excessive mercury consumption can lead to mercury poisoning, which can cause numbness, tremors, vision problems, seizures and other neurological issues.
Macronutrients in High-Protein Diets
Eating just protein would be a bad idea, as you need fats and carbohydrates as part of a healthy diet. While carbohydrates often get a bad reputation due to their association with refined and processed foods, carbohydrates also include fiber — an important nutrient for your digestive system. You can find carbohydrates in many foods, like fruits, vegetables, grains, nuts and seeds.
According to the Mayo Clinic, carbohydrates should typically make up the majority of the macronutrients in your diet. This means that between 45 to 65 percent of your calories should come from carbohydrates, which results in people consuming anywhere from 12 to 20 percent of their daily calories from protein.
Protein Consumption and Weight Loss
Increasing protein intake while reducing the consumption of other macronutrients has been shown to promote weight loss. High-protein, low-fat diets have also been shown to:
Notably, high-protein diets are often able to achieve many of these improvements in health even when the people who follow them are primarily sedentary.
According to a 2015 study in the American Journal of Clinical Nutrition, between 1.2 and 1.6 grams of protein per kilogram of body weight is the ideal amount of protein for weight loss. Ideally, when you consume this much protein, it should be dispersed in various meals in portions of 25 to 30 grams. This essentially means that, while increased amounts of protein can support weight loss, you shouldn't eat only protein.
Recommended Dietary Amounts of Protein
According to the Food and Drug Administration, most people should consume about 50 grams of protein per day. However, the USDA's Recommended Dietary Allowance (RDA) for protein is based on your weight. To calculate your individual RDA for protein, you can allow 0.8 gram of protein for every kilogram you weigh.
The average American man weighs 195.7 pounds (or 88.77 kilograms), and the average woman weighs 168.5 pounds (or 75.21 kilograms). Based on the RDA, this means that the average man should consume 71 grams of protein each day, and the average woman should consume 60 grams. To figure out your RDA for protein, all you need to do is multiply your weight in kilograms by 0.8.
Eating Primarily Protein
Eating only protein and vegetables would be difficult, but not impossible. However, you should be aware that it's hard to avoid fat since many foods naturally contain fat.
Protein sources, particularly those that come from animal and marine products, usually contain some amount of fat. Eggs, nuts, seeds and even avocados also contain fat. Most people tend to cook with a fat source as well — although this fat may come from healthy vegetable-based oils. Fortunately, many of these are healthy fats, like the omega-3 fatty acids found in fatty fish and the omega-6 fatty acids found in nuts and seeds.
If you want a diet that focuses on high-protein, low-fat foods, you should focus on consuming lean meat and vegan-friendly protein products. Popular vegetarian sources of protein, like dairy products, may have more fat than you want to consume. However, it is possible to obtain fat-free or low-fat dairy products, like skim milk or light cheeses.
Dietary Sources of Protein
There are many sources of protein for meat eaters, pescatarians, vegetarians and vegans. Vegans are the most restricted as their protein exclusively comes from plant-based sources. Good plant-based proteins include:
- Beans, peas and other legumes
- Seitan, which is made from vital wheat gluten
In addition to these plant-based sources of protein, vegetarians also have other sources of protein available to them, including:
- Eggs, which can come from birds like chickens, ducks and quails
- Dairy products, such as milk, cheese and yogurt
Many pescatarians eat dairy and eggs. Those who don't would simply avoid dairy and eggs, but would still consume plant-based sources of protein. All pescatarians would also consume seafood products like fish, shellfish and mollusks. These marine products are typically their primary source of protein.
People who eat meat have the most obvious sources of protein available to them. In addition to all the other protein-rich foods, meat-eating people can eat such animal-based proteins as:
- Game meats, like deer, grouse, pheasant and rabbit
- Journal of the International Society of Sports Nutrition: The Effects of Consuming a High Protein Diet (4.4 G/Kg/D) on Body Composition in Resistance-Trained Individuals
- Food Functionality: Dietary Protein Intake and Human Health.
- Centers for Disease Control and Prevention: National Center for Health Statistics: Body Measurements
- Food and Nutrition Board, Institute of Medicine, National Academies: Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Total Water and Macronutrients
- Food and Drug Administration: Protein
- The American Journal of Clinical Nutrition: The Role of Protein in Weight Loss and Maintenance
- The American Journal of Clinical Nutrition: Effects of Energy-Restricted High-Protein, Low-Fat Compared With Standard-Protein, Low-Fat Diets: A Meta-Analysis of Randomized Controlled Trials
- The American Journal of Clinical Nutrition: High-Protein, Low-Fat Diets Are Effective for Weight Loss and Favorably Alter Biomarkers in Healthy Adults
- Culinary Nutrition: The Science and Practice of Healthy Cooking: Chapter 10 - Weight Management: Finding the Healthy Balance: Practical Applications for Nutrition, Food Science and Culinary Professionals
- Kaiser Permanente: Balancing Carbs, Protein, and Fat
- Mayo Clinic: Carbohydrates: How Carbs Fit Into a Healthy Diet
- Popular Science: Please Do Not Try to Survive on an All-Meat Diet
- The Dukan Diet: The Revised and Updated Edition for 2019
- Annual Reviews: Can We Say What Diet Is Best for Health?
- European Journal of Clinical Nutrition: Metabolic and Physiologic Improvements From Consuming a Paleolithic, Hunter-Gatherer Type Diet
- American Association for the Advancement of Science: Greenlandic Inuit Show Genetic Signatures of Diet and Climate Adaptation
- MedlinePlus: Mercury Poisoning