hegemo 

Physical health is impacted by environment, nutrition, mental health, fitness, and all the stages of Maslow's Hierarchy of Needs which increase and decline as humans growth and decline into obscurity.

We only have to recall the statements made by health practitioners a few years back to recognise how important being outside and getting exercise is (which either was or shall be explained in a different part of a different question, I think). However, from an earlier answer: There is more oxygen and less carbon dioxide outside so getting exercise outside is better than inside. Besides that, physical exercise releases endorphins/serotonin/dopamine that make people feel mentally good. 

If individuals feel physically good, medical professionals think that those individuals feel mentally good and are more effective in dealing with everyday mental stresses.

Physical health includes rest / recuperation and sleep, nutrition and lifestyles, but these are dealt with in other segments of this question. However, poor health can lead to embarrassment, anxiety, and stress, as well as causing time off work (which may actually improve mental well-being) that could result in worry, isolation, and depression. Some people curl up in bed when they are physically unwell which can mean that they spend a reduced amount of time cleaning their home; a cluttered home can lead to mental unwellness.

Introducing chemicals in the body in amounts that are beyond the amount the body can create itself can lead to an impairment to mental health. For example, the stomach, as a by-product creates alcohol in small amounts, yet imbibing alcohol will necessarily deplete necessary chemicals and minerals in the body. Nicotine inhibits dopamine production, which is a chemical in the brain that makes people feel mentally good. However, further discussion of nutrition is wasted here as it is better utilised in a different segment of this same question.
 

Nutrition

The human body needs elements, nutrients, compounds, water, and more, to not only survive but also to function in order for it to continue to survive, and this requires the body to maintain itself. Not getting the right elements, nutrients, chemical compounds, water, and the rest of the stuff the human body needs will cause it to not function as well as it should for peak performance. That is not to say that removing any one of the thousands of compounds that an individual should normally have in a balanced diet will cause a catastrophic decline into a state of mental ill health. Yet, we all know that simply by removing just oxygen, or water, will kill any human. Having a poor diet will leave people feeling tired and lethargic which ultimately leads to moods that are less than normal. Low mood, if sustained, leads to poor mental health, which as we know, can be only the first step in a chain of mental ill health. Regular eating of the right foods maintains a stable blood sugar level which helps to maintain an even level of mood and energy levels.

The B vitamin complex is responsible for good nerve condition and cognitive function. Deficiencies of vitamin B12 will result in significant cognitive dysfunction, such that the beliefs of the person with low B12 levels will seem very strange to others. This is a vitamin that vegetarians and vegans are expected, by most of the public, to miss out on. Indeed they do, in our modern society of supermarkets and mass consumption. Of course, the remote tribes are not all loonies so they must know how to get B12 from somewhere. Generally, meat-eaters will get their dose of B12 and B6 from the animals they have killed or bought. It is quite common for people in the Global North who eat meat to, when they discover that someone they are talking to, or have overheard, is showing signs of mental aberration to think that the person is odd or a little mad, Yet, when they discover that, that person is a non-meat-eater, they will immediately blame that person's diet for the problem, or at least set up a short circuit of thinking that comes up with - Vegan/Vegetarian = crazy, or vice-versa. Indeed, that could be correct. There is a great misunderstanding in the general public that sometimes correlation really is cause. Such like, an individual has low moods, and is overweight (Notwithstanding that an individual who is concerned about their weight might feel low, or the overweight is due to lack of positive exercise). Maybe, though, lots of cheap simple carbohydrates and not a lot of expensive meat makes you sad and fat. Manufacturers don't add vitamins and minerals to breakfast cereal, nearly all expensive but containing lots of portions, just to get rid of them instead of throwing them away..
 

Healthy lifestyle

While a healthy lifestyle is of course a temporary factor, it also falls into the category of being a long-term factor, and an internal environmental factor and an external environment. It also includes nutrition, physical exercise, mental exercise, must include a comparison to different cultures (historical and modern), and a comparison between being inside and being outside and the duration and frequency of being inside or outside and the physical durability and fragility of a person to withstand certain climates, geographical and topological environments such as a person's maturity or genetic ancestry and including a long-term normal lifestyle in particular cultures that exist in certain environments across the world.  Almost all of these factors appear in other answers given. However, I will try not to repeat myself and only cover the areas I have not clarified or are available in other pages

A healthy lifestyle is usually considered (correctly) to have any impact when it is a long-term health condition: This is included in all the other segments of this question; 4a, 4b, 4d, and 4e. All answers that students have written in this segment should at the very least be in answer 3d. This is because we say that we live healthily as meaning the present, and reserve lifestyle to describe the past and present as a long-term living style simply because the word 'life' means from beginning to end of an organism living period. However, a life can be very, very short, measured in minutes, hours, right up to millennia. Rightly, we would consider a lifestyle to reflect a period of living that is relative to the age of an organisation when it dies. It would not be right to say that a university student led a lifestyle of going to parties and getting drunk that can be described as a poor lifestyle without also attaching to that period a reason for the frivolity, or how long the period extended, in other words, qualifying the length of time a lifestyle lasted, even if it includes suppressed premises. In the case of the student, the lifestyle is the length of the university attendance and that period needs to be expressed. It is not enough to say that one had an unhealthy lifestyle without qualifying the length of the lifestyle when lifestyle is not the length of the human’s life. In essence, my own lifestyle has includes periods of excellent fitness, poor diet, too much alcohol, excellent and fine food, poor sleep patterns, easy living, etc. These apply to the length of my life so far.

Rest / Sleep

Rest and sleep is part of a healthy lifestyle which by definition includes not abusing the body, and getting plenty of outside exercise and having a good social life (all of which are discussed elsewhere in other segments of other questions over and over again).

Poor sleep can make people feel irritable, but it is obvious that poor sleep is a vicarious result of another symptom. Good sleep, on the other hand, allows the body to repair itself and so allow positive physical exercise that in turn promotes good sleep. 

Poor sleep can impair memory and thinking processes which can be a risk factor for mental ill health.

Long-term health conditions:

Any person who is in near perfect physical health who cannot acclimatise to the low oxygen content of the high Andes regions in order to be able to satisfactorily compete with the local population who are genetically better able to cope with the thin air will in all likelihood feel ostracised by the locals for being lazy or unproductive, or they will feel pitied for being weak and fragile. So, a long-term near-perfect health condition can produce feelings of negativity or affect social intercourse. Otherwise, we must consider long-term health conditions to be an inadequately-formed subjective concept, or at least a slippery concept, if we omit whether we want to discuss either good or bad health conditions, make comparisons between them, and foolishly ignore cultural differences which favour some people over others in certain climatic environments or people will specialised abilities either naturally or by training.