Life is fleeting and our days on earth are limited, so we need to do the best we can with the one life we have been given.
King David prayed to God: "Show me, O LORD, my life's end and the number of my days; let me know how fleeting is my life." (Psalm 39:4) Furthermore, God said to Solomon in a dream, "If you walk in my ways and obey my statutes and commands as David your father did, I will give you a long life." (1 Kings 3:14) This indicates that if we live in harmony with God's Word, will, and ways (which includes healthy living habits), under normal circumstances we can lengthen our life. Also the fifth of the Ten Commandments says, "Honour your father and your mother, so that you may live long in the land the LORD your God is giving you." (Exodus 20:12)
On the other hand, there is no doubt that we can shorten our life by not living in harmony with God's ways, through an unhealthy diet, lack of exercise, nursing grudges, an unforgiving spirit, unresolved super-charged repressed negative emotions, impaired relational conflicts, too much stress and anxiety, addictive behaviours and/or substances, and any of a score or more of other unhealthy habits and ways of living.
Suggested prayer: "Dear God, please help me to so live in harmony with your will and the principles for healthy living as found in your Word, that my life on earth will be healthy, long, and fruitful for the glory of your Name. Thank you for hearing and answering my prayer. Gratefully, in Jesus' name, amen."