A 12 week diet can have a significant effect on your body composition and your overall health. If your plan is to lose fat, you'll be able to make a significant dent in any weight problem. If your plan is to gain muscle, 12 weeks is easily long enough to achieve a noticeable difference in your physique. If you simply are dieting to get healthier, you'll notice a difference within this time period too.
12 Weeks to Weight Loss
With 12 weeks of dieting for weight loss, you can expect to lose between 12 and 24 pounds. To start, keep a record of the types and amounts of food and drink that you consume over the course of a preliminary week. Use the relevant nutritional information to calculate your average daily caloric intake. Depending on your the urgency of your plan, aim to reduce your daily caloric intake by between 500 and 1,000. Over the course of each week, this will sum to between 3,500 and 7,000 calories of deficit. According to the Mayo Clinic, since 3,500 calories is roughly equivalent to one pound of fat, this will allow you to lose between one and two pounds per week. To satisfy the deficit requirement, start by eliminating simple carbohydrates such as sweets, desserts and sugary drinks from your diet. If you've got more reduction to go, proceed by reducing the sizes of your mealtime portions as necessary.
12 Weeks to Muscle Gain
Building muscle is generally a slower process than losing fat, and individuals vary greatly in their ability to build muscle. Still, given ample calories and protein, significant changes are possible over 12 weeks. Since your time is limited, don't take any chances at under-nutrition; aim to consume at least 4,000 calories and at least 1.6 grams of protein per kilogram of body weight each day, according to "The Journal of the International Society of Sports Nutrition." In order to achieve this, increase your feeding frequency to between five and seven meals per day. Base each of these meals around one of more protein-rich staples, including meats, fish, eggs, beans and tofu.
12 Weeks to General Health
If you're satisfied with your body weight and composition, 12 weeks is not so much a time constraint as a motivational goal. While eating healthy for optimal vitamin and mineral intake isn't necessarily easy or pleasant, after 12 weeks of consistency you'll be used to the diet and you'll have noticed results. To determine your ideal dietary values--customized for your gender, age, weight and body structure--consult the U.S. Department of Agriculture's American food pyramid. This will provide you with your ideal daily values for meats, grains, dairy, vegetables and fruits.