4 physical signs you need to eat more protein, from brittle nails to aching muscles

• Protein is essential to keep the body functioning optimally.
• If you're not consuming enough, you might lose muscle, and struggle to recover from workouts.

Protein is an essential macronutrient needed to maintain health, and which every cell in our body needs to function correctly.

In the Western world, it's rare for people not to meet the "relatively low" recommended US daily intake of 50 grams, dietitian Nichola Ludlam-Raine told Insider, but individual requirements for optimal functioning vary depending on activity levels, dietary pattern, age, and fitness goals.

If you are active or trying to lose body fat, fitness professionals recommend increasing your protein intake up to 0.9 grams per pound of body weight, spreading intake evenly over the course of the day.

For someone weighing 160 pounds, this means consuming up to 144 grams of protein a day.

Protein is satiating, has a higher thermic effect than fat and carbs (meaning the body uses more energy digesting it), aids muscle maintenance while a person is losing fat, and helps muscles recover from workouts.

If you don't eat enough protein, you may lose muscle; have weak skin, hair, and nails; feel more hunger; and struggle to recover after exercise, Ludlam-Raine said.

She told us the four physical signs you might not be consuming enough.

Muscle loss

Muscle mass naturally starts to decrease after the age of 40 (known as sarcopenia), so getting enough protein as you age is particularly important, Ludlam-Raine said.

This is why protein requirements are higher for older adults: Researchers in the field of protein and aging recommend consuming 1.2 to 2 grams of protein per kilogram of bodyweight per day (or higher) for elderly adults, which is about the same as what's recommended for active adults.

"If you follow a particular dietary pattern such as a vegan diet and/or are reducing your calorie intake for weight loss, there is an increased risk of loss of muscle mass alongside fat, which is why it's important to have a source of protein in each of your daily meals," Ludlam-Raine said.

Weak skin, hair, and nails

If your hair and nails are weak and your skin has lost elasticity, it could be a sign you're not eating enough protein.

"A lack of protein in the diet can cause hair and nails to become brittle and more susceptible to damage, as proteins (such as keratin) play an important role in the structure and function of the cells that make up the body's organs and tissue," Ludlam-Raine said.

Protein helps maintain skin strength too, according to research.

Increased appetite

If you struggle with hunger, it could be that you're not eating enough overall, or that you're not eating enough protein.

"Protein is the most satiating nutrient in comparison to carbohydrates and fats, and therefore if you have a lack of protein in your diet, you may find it more challenging to feel as 'full' after a meal," Ludlam-Raine said.

Poor exercise recovery

If you find your body takes a long time to feel OK again after exercise, it could also be a sign that your protein intake is too low.

"Protein is needed for growth and repair, so if you aren't getting enough protein post-exercise, in particular after doing strength exercises, your muscles' ability to grow and recover before your next workout is reduced," Ludlam-Raine said.

This can manifest as muscle soreness and fatigue, which means you may struggle to perform your best in future workouts.

Protein isn't just important after workouts, though — it's best to consume some at regular intervals over the course of the day, research suggests.