Directionally right, but not entirely correct. Scroll to the bottom of my post.
Let's first address this protein fixation - consider a typical male human being height 170 cm - weight 65 kg having 15% body fat. Most likely a person with higher weight than this will carry excess fat, this doesn't change the protein calculations.
How much protein is required? Proteins can be used as fuel for cells, or can be used to repair the cells, or to build something new (e.g. child's or teenage growth).
For an adult, who has stopped his growth spurt, and the only other growth he can undergo is a measly 2-5 kg of muscles due to weight training or 10-20 kg muscles due to exogenous anabolic hormones. Going back a few lines, a teenage undergrowing growth spurt would require more protein or an adult whose only growth happens at waistline?
For an adult what is the lower limit? Easy to determine, eliminate protein from diet, and observe & record the nitrogen loss happening from the body. All nitrogen loss is result of cellular breakdown - and this is the amount of protein necessary to maintain the body healthily. You can refer more details here:
https://www.ncbi.nlm.nih.gov/books/NBK234922/
The net outcome is that
0.6 g of protein per kg per day is average adult requirement for sustaining normal life. Since humans beings have some variability, and it is always safe to adhere to upper limit rather than lower, this number is 0.75 g of protein per kg per day. The recommended (safe to publish and circulate among lesser educated) figure (
RDA) is even higher at 0.85 g/kg/day.
What about upper limit? The fastest growing organism is the one present inside the womb. The next fastest growth is when it is outside and is infant.
1.73 g/kg/day is the average recommendation around 3-6 month's period based on observation of mother's lactation and growing infant's diet.
Then there are complications caused by biological factor and digestibility, summary: milk, eggs, non-veg sources are more efficient than veg sources. You may even need to eat double qty veg protein to be similar to eggs. Let's take an average of 70% as the vegetarian (in)efficiency.
So now we are coming to the point that 0.85/.7 = 1.21 g of veg protein per kg per day.
My average guy is 65 kg, hence his required intake = 79 grams
If we do the same calculation for lower limit 0.6/0.7 = 0.86 g of veg proteins per kg per day X 65 kg = 56 grams
Anyone telling you anything else is just trying to sell protein powder to you without understanding the experimentational science that has led us to these figures.
Now coming to vegetarian diet. One of the poorest wholemeal protein sources is rice. Raw rice is 7% proteins (and 3.65 kcal/g).
I am using raw items here because nutritional profile is easily comparable for raw. Cooking hydrates the food, and different items absorb different amount of water. However, water doesn't change the protein or calorie calculations because it has neither.
In order to meet the 79 grams recommendation, I will have to eat 79/.07 = 1.1 kg of (raw) rice per day. This will provide me with 4116 kcal, enough to make me fat very fast.
In order to meet the 56 grams minimum requirement, I will need to eat 56/.07 = 796 g of (raw) rice per day. This provides me with 2905 kcal, still on slightly higher side but if I am physically active this could easily be maintenance calories.
What about richer source of protein? Say pulses / legumes. Mung/masoor/toor/urad - typical (raw) dals in Indian household have around 20-25% protein (and 3.5 kcal/g). Let's run the same calculations once again:
In order to meet the 79 grams recommendation, I will have to eat 79/.2 = 395 g of (raw) legumes per day. This will provide me with 1381 kcal, barely sufficient to let me live.
In order to meet the 56 grams minimum requirement, I will need to eat 56/.2 = 279 g of (raw) legumes per day. This provides me with 975 kcal, I will surely die.
What this suggests is that if I need to satisfy my calorific requirement of 2500 kcal/day, I will need to consume around 714 g of raw legumes, which also ends up providing me with 143 g of proteins!
The wholemeal vegetarian truth lies somewhere between these two extremes
(we anyway have a mix of rice and dal everywhere across the world) - thus I am confident in stating that a person will have neither protein deficiency, nor have excess calorie consumption.
*phew* Its been a long post, I had zero intention and focus to do this, but it needs to be done. There are so many misconceptions being floated by social media idiots/influencers and steroid junkies at the gyms that they have changed the entire narrative about nutrition just to peddle their stuff.
But I am certain that the next page of this thread will again have some juvenile questions and outlandish claims fueled by confusion caused by social media and gym bro'hood.