When I first became serious about Christianity and was baptized, I didn't get fasting at all. About this same time, anorexia became commonplace and even trendy among young women. I fasted often, even 2-3 days per week, but it wasn't real fasting. Because it wasn't done to increase my spirituality, it was only extreme dieting. Although fasting is difficult, I highly recommend it for the following reasons.
"On one occasion, the Savior cast a devil out from a child and used this experience to teach His disciples about the
power of prayer and fasting. His disciples asked Him, “Why could not we cast him out?” Jesus answered: “Because of
your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain,
Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you. Howbeit this kind
goeth not out but by prayer and fasting.” (See Matthew 17:14–21.)
This account teaches that prayer and fasting can give added strength to those giving and receiving priesthood
blessings. The account can also be applied to personal efforts to live the gospel. If you have a weakness or sin that
you have struggled to overcome, you may need to fast and pray in order to receive the help or forgiveness you desire.
Like the demon that Christ cast out, your difficulty may be the kind that will go out only through prayer and fasting.
You can fast for many purposes. Fasting is one way of worshiping God and expressing gratitude to Him (see Luke 2:37; Alma 45:1). You can fast as you ask Heavenly Father to bless the sick or afflicted (see Matthew 17:14–21). Fasting may help you and those you love receive personal revelation and become converted to the truth (see Alma 5:46; 6:6). Through fasting you can gain strength to resist temptation (see Isaiah 58:6). You can fast as you strive to humble yourself before God and exercise faith in Jesus Christ (see Omni 1:26; Helaman 3:35). You may fast to receive guidance in
sharing the gospel and magnifying Church callings (see Acts 13:2–3; Alma 17:3, 9; 3 Nephi 27:1–2). Fasting may accompany
righteous sorrow or mourning (see Alma 28:4–6; 30:1–2)." True to the Faith