Entrepreneurs often struggle to maintain healthy diets, whether they're skipping breakfast to get a jump on morning emails or overeating after a hectic day. But proper nutrition is essential for business success, according to Barbara Mendez, a nutritionist who works with many entrepreneurs. Sure, eating right makes you look and feel better, Mendez told a crowd at the Inc. 5000 conference. But it also helps you stay focused and energized during the day, which is key when you're running your own company. Here are three of Mendez's tips for doing just that.

1. Don't skip breakfast.

Most entrepreneurs skip breakfast or grab a coffee, donut or bagel on the fly, Mendez says. If you skip breakfast, if you're like most people, you may begin to lose focus and energy within three hours. If you eat a donut, bagel or other refined carbohydrate for breakfast, it's likely that you'll lose focus and energy one to three hours later. 

The ideal breakfast for long-lasting energy and concentration? A vegetable omelette with a side of tomatoes and greens. Why? Protein gives your body a sustainable source of fuel to keep you going throughout the day. Since you don't excrete insulin after eating protein, you stay focused and energized for five to six hours and experience fewer sugar cravings.

Another good option is plain oatmeal with a touch of cinnamon, almonds or walnuts, and flax seed. You can also try a smoothie made with blueberries, flax seed oil and almond butter. Mendez recommends using almond milk instead of yogurt, which adds lactose and calories.

2. Eat a 4 p.m. snack.

Having a snack a few hours after lunch sustains your energy level through the end of the day. It also cuts down on overeating at dinnertime, which can disrupt your sleep. Mendez recommends snacking on a apple slices dipped in almond butter, which provides protein and fat needed for sustained energy. Other good options include hummus and carrots or a small smoothie. 

3 Get a good night's rest.

Overeating at dinner or snacking late into the night often leads to disjointed sleep, since your body is working hard to digest food. Instead, have a light meal and stop eating three hours before bedtime. Mendez also suggests writing down the three best things about your day--and three things you plan to do tomorrow--to induce a feeling of calm before bedtime.
Top on your to-do list for tomorrow? Eat a healthy breakfast, of course.
For more tips about sleeping from Mendez, check out "7 Sleep Habits of Successful Entrepreneurs."