Protein, Fibre and Fruit and Veg are all essential parts of a healthy, well fuelled diet - whether we have a weight loss goal or want to eat well. Here are the links to the studies and sources I mentioned that give guidance on how much of these things we need
Protein:
Meta analyses from Morton et al. (2017) and Tagawa et all (2022), conclude the amount should be between 1.5-2.2g per kg of lean bodyweight. The lower end of this around 1.6g/kg would be a suitable amount for most people
Fibre:
The recommended amount is 30g per day for adults
NHS info on fibre - how much we need and how to get more
Fruit & Veg:
5 Fruit and veg a day are the common guidelines we often hear.
Meta-analyses show 5 a day for reducing mortality risk, and chronic diseases such as cardiovascular disease and cancers. Source: Fruit and vegetable intake and risk of cv disease, total cancer and all cause mortality
There is research to show that 5 portions of fruit & veg are recommended for disease prevention and around 7 are recommended for getting the micronutrients we need (e.g. folate, vitamin a, c and d, potassium, magnesium..)
Source: Fruit and vegetable intakes meeting the dietary reference intakes of Japanese adults.