I see two types of eating habits by triathletes the week prior to a race.
1) Athletes who load up on carbs in order to ensure that they don't run out of fuel on race day.
2) Athletes who avoid certain foods or cut back on daily calories in order to prevent weight gain.
I rarely see athletes enter race week without some uneasiness about their nutrition or body composition. I think it is great that I can be on both sides of the equation. As a competitive athlete and sport nutritionist, I don't only try to understand why other's have problems but I have to figure out my own nutrition as well. I have been both athletes so I know how hard it is to feel confidence about the foods you are eating and how your performance will turn out come race day.
As far as loading up on carbs on race week, remember that you are cutting back your training volume (yet keeping the intensity with more rest) in order to properly rest your body. Because stored glycogen (carbs) aren't being used in a high quantity to fuel intense and/or long workout, you have no reason to over-eat on carbs. However, it is important to watch your fat intake (focus on unsaturated fats for good fats to keep you satisfied and full) the 3 days leading up to a race in order to ensure that you are getting a good amount of carb and protein calories, rather than calories from fat (1g carbs/protein=4 calories, 1g fat=9 calories). Focus on your daily diet calories (around 1800-2200 for women, 2400-2800 for men..all dependent on training volume and intensity) and add in more snack calories, rather than bigger "carbo-load" meals. Meals should be around 400-500 calories and snacks around 150-200 calories on a daily basis. However, come race week, add in one or two additional 100-200 calorie snacks in the form of carbs and protein. For example, if you favor a certain bar, have 1/2 sports bar (always keep bars less than 220 calories and avoid loads of sugar alcohols or icy coatings) and milk or fruit and whey protein. Other options could be toast w/ cheese, a smoothie or yogurt and nuts. Because no one wants extra calories to be stored as fat, portion controlled meals and small, frequent snacks will help promote glycogen storage rather than excess calories stored as fat. Most of all, to help your self-confidence since every athlete wants to go into a race feeling good about their strong, trained body, remember that the extra carbs that you are storing for fuel will bring in extra water. So if you are feeling a little heavy the days before the race, know that you are well-fueled and that you didn't go overboard by loading your body with too many calories. Glyocgen storage in the muscles max's out around 2,000 calories. If you take in account your resting metabolism (which accounts for 65-75% of daily calorie expenditure, exercise only accounts for only around 20-30%..the rest is from absorption and digestion of food), a daily diet with around 60-75% carbs (higher range the 3 days leading up to a race) will give you plenty of fuel come race day! Don't forget the pre race dinner which should be high in carbs, but eaten 2 nights before race day morning (smaller dinner, of the same food, should be eaten the night before a race so that the smaller meal can be easily digested and the bigger meal will have time to pass through the body).
As far as the other athlete, I hear it all the time. You want to go into a race with a different body than what you have. 1 or 2 weeks isn't enough time to trim fat and turn the body into a lean machine. It takes months to lose weight in a healthy way, especially if you wish you could be 10-15 lbs lighter. If you are wishing to be 3-5 lbs lighter you are risking the chance of poor performance, lack of energy and a possible risk of injury by cutting back on daily calories. Losing weight takes time (in addition to discipline). I know triathletes don't sign up for a big race 2-weeks before the race and expect to have a great performance. Training the body to perform at a higher treshold takes time. It is very important that if you want to lose weight that you start well before a race. I know it is hard to go into a race with a body that you don't like, but you must like what the body has allowed you to do. You have pushed hard, you have gone the distance and I know you have felt strong as you trained for your race. Rather than worrying about your body weight or image (things that you can't change in 1 week) think about how you will pull out a great performance or achieve a goal. I find it interesting that athletes procrastinate on weight loss yet are so strict on training. There are lots of nutrition excuses when it comes to training and just because you "burned it off in training" or are "getting ready for a big weekend of training" you must be accountable of what you are really eating. Cutting back on 200-300 calories a day for 2 months can dramatically change your body image. However, cutting back on 200-300 calories the week before a race can dramatically hurt your performance.
Enjoy your race week and focus on a well-balance diet of carbs, protein and fat and be sure to combine protein with carbs to keep your blood sugar balanced the days leading up to a race. In addition to eating every couple of hours, be sure you have practiced your race day morning breakfast. Be confident with your nutrition and take pride in your body which will bring you to the finish line. Afterwards, enjoy a day to recover and indulge in a 200-300 calorie healthy desert (avoid indulging in high fat, high calorie foods for a week straight). The day after the race, you can start your weight loss by focusing on what steps you will take to reach your goal weight come the next race.