diet_plan.rb

def ask_question question
  print "#{question} "
  return gets.chomp
end

def ask_exercise_level
  puts "What's your exercise level (1-5)? "
  puts '  1. little or no exercise'
  puts '  2. exercise/sports 1 - 3 times per week'
  puts '  3. exercise/sports 4 - 5 times per week'
  puts '  4. exercise/sports 6 - 7 times per week'
  puts '  5. very hard exercise/sports or physical job'
  return gets.chomp
end

def calculate_bmi(weight, height)
  weight / (height / 100.0)**2
end

def calculate_ideal_weight(bmi, height)
  (0.5 * bmi + 11.5) * (height / 100.0)**2
end

def calculate_bmr(weight, height, age, gender)
  bmr = 10.0 * weight + 6.25 * height - 5.0 * age
  bmr += 5 if gender == 'm'
  bmr -= 161 if gender == 'f'
  return bmr
end

def calculate_cal_per_day(bmr, exercise_level)
  cal_per_day = bmr
  cal_per_day *= 1.2 if exercise_level == '1'
  cal_per_day *= 1.375 if exercise_level == '2'
  cal_per_day *= 1.55 if exercise_level == '3'
  cal_per_day *= 1.725 if exercise_level == '4'
  cal_per_day *= 1.9 if exercise_level == '5'
  return cal_per_day
end

def diet_plan(weight, ideal_weight, cal_per_day)
  if weight > ideal_weight
    diet_cal_per_day = cal_per_day - 500
    diet_weeks = (weight - ideal_weight) / 0.5
  else
    diet_cal_per_day = cal_per_day + 500
    diet_weeks = (ideal_weight - weight) / 0.5
  end
  return diet_cal_per_day, diet_weeks
end

puts "Welcome, let's create you a diet plan!"
puts ""

age = ask_question("What's your age (years)?").to_i
height = ask_question("What's your height (cm)?").to_i
weight = ask_question("What's your weight (kg)?").to_i
gender = ask_question "What's your gender (m/f)?"
exercise_level = ask_exercise_level

bmi = calculate_bmi weight, height
ideal_weight = calculate_ideal_weight bmi, height
bmr = calculate_bmr weight, height, age, gender
cal_per_day = calculate_cal_per_day bmr, exercise_level

diet_cal_per_day, diet_weeks = diet_plan(weight, ideal_weight, cal_per_day)

goal_bmr = calculate_bmr ideal_weight, height, age, gender
goal_cal_per_day = calculate_cal_per_day goal_bmr, exercise_level

puts "\nYour ideal weight is #{ideal_weight} kg. To reach this weight you should be consuming #{diet_cal_per_day} calories per day for #{diet_weeks} weeks."
puts "When you've reached this weight you should adjust your diet to contain #{goal_cal_per_day} calories per day."