We asked a dietitian what you should -- and shouldn't -- do if you want to look and feel healthier in a week

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There are plenty of things you can start doing right now to feel healthier in one week.

Sure, you’re probably not going to wake up looking like an underwear model tomorrow — but you can certainly start feeling better and improving your digestion in a week, according to registered dietitian and nutritionist Andy Bellatti.

Here are a few things Bellatti and other nutritionists recommend.

DO: Drink lots of water.

Water is essential -- it regulates the shape of every cell inside our bodies. If we don't get enough, in fact, these cells begin to shrivel up.

The Centres for Disease Control and Prevention recommends choosing water instead of sugar-sweetened beverages to 'help with weight management.' Swapping a cold glass of H2O for a single 20-ounce soda will save you about 240 calories.

So hydrate, Bellatti told Business Insider. 'Ideally with water.' Not a fan of the absence of flavour? He suggests spicing it up with a few slices of lemon, lime, or cucumber.

DON'T: Drink only water -- or any other beverage.

If you're considering a 'detox' or 'juice cleanse,' you might want to reconsider. Drinking just water, juice, or any other liquefied concoction for more than a few days can set you up for unhealthy eating behaviours, and can often lead to unhealthy spikes and drops in blood sugar levels, which can spawn cravings and mood swings.

'This is a recipe for 'hangriness,'' says Bellatti, 'that also inaccurately paints all solid food as problematic.'

DON'T: Start banning a bunch of food groups.

There's a difference between cutting back on things you eat in excess and banning certain food groups entirely. Diets that rely on avoiding ingredients (like sugar or gluten) can lead to replacing those things with other ingredients that play the same role in the body (like honey or corn-based foods). Doing this can be dangerous if the replacement products are nutrient-deficient.

DO: Fill up with fibre.

Writer Michael Pollan said it best: 'Eat food. Not too much. Mostly plants.'

Fresh, high-fibre vegetables like broccoli, bell peppers, and Brussels sprouts -- which the CDC actually calls 'powerhouse foods' -- are a great source of key vitamins and nutrients, including fibre, which helps keep you feeling full and satisfied until your next meal.

'Whole, plant-based foods (fruits, vegetables, whole grains, beans, nuts, and seeds) are best,' says Bellatti. 'One quick way to add extra fibre to your day: sprinkle chia, hemp, or ground flax over whatever you're eating for a boost.'

DON'T: Rely on powders and pills.

The problem with diet powders and pills, says Bellatti, is they often take something that was once a whole food, like a fruit or a vegetable, and then separate and process it for one ingredient. That's OK for things like cocoa powder, which does have nutrients, but it shouldn't make up the bulk of your eating regimen.

'When something is a powder, you're probably using what, a teaspoon or tablespoon at most? And you have to wonder how much that can really do. Versus a cup of broccoli or a quarter cup of cashews. That's something significant,' says Bellatti.

DO: Be mindful of portion sizes.

The baseline portion sizes of our snacks and meals have ballooned -- even the plates and cups we serve them on have gotten noticeably bigger.

The average size of many of our foods, whether its fast-food, sit-down meals, or even items from the grocery store, has grown by as much as 138% since the 1970s, according to data from the American Journal of Public Health, the Journal of Nutrition, and the Journal of the American Medical Association.

So be mindful of portion sizes, and if you're eating out, consider taking some of your meal to-go for later.

DON'T: Focus exclusively on calories.

Focusing exclusively on calories can be dangerous.

'This is especially true when eating at restaurants,' says Bellatti. 'Many low-calorie items are loaded with sodium, which retains water and can leave you feeling bloated.'

Plus, keep in mind that for sustained weight loss, you're only supposed to lose about 1-3 pounds each week, Philip Stanforth, a professor of exercise science at the University of Texas and the executive director of the Fitness Institute of Texas, told Business Insider. 'That tends to be a lot more sustainable than losing a whole bunch at once,' says Stanforth.

DO: Think positive.

Thinking positively about eating and feeling better can help motivate some people to stick to a new lifestyle.

'In terms of changing the way you eat (it's much more than a 'diet'), focus on the opportunities and what you can eat as opposed to what foods you're trying to cut down on,' Dr. Donald Hensrud, who chairs the Mayo Clinic's division of preventive, occupational and aerospace medicine writes in a blog post for the Clinic. 'There are many wonderful foods and recipes to explore, and believe it or not, we can learn to like new foods.'

DON'T: Expect miracles.

Let's be real: Eating right for a week isn't going to counteract decades of subsisting on fries and Frappuccinos. But it is enough to reduce some of the more irritating aspects of those symptoms -- the bloating linked with a high-salt diet, the fatigue associated with blood sugar crashes.

'The most that can happen in a week's time is that you make choices that help reduce bloating and puffiness. Any promises beyond that are more about marketing and hyperbole than anything else,' says Bellatti.

More important, though, committing to treating your body well (if even only for a few days) might be enough to lay the foundation for months or years of future healthy eating. If you can prove to yourself that you can treat your body right (and that it feels good to do so!) you just might be more likely to keep doing so later on.

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