Why not try a  nutritious shake which will give you the necessary nutrients without causing your blood sugar to go high . These shakes are low glycemic which means they will turn to sugar slowly after consuming. Since you wish also to put on some weight these may be the right kind of drinks you need when you take it into between your meals.

They come in 3 flavors - chocolate, strawberry and vanilla. They are packed in convenient sachets which you you can reseal easily- convenient to keep in the office.

Pack a lunch
Packing a lunch not only saves you money, but you'll also have complete control over what you eat each day.

Choose healthy options when out for lunch with co-workers
At a business lunch? Most restaurants should have a healthy choice like chicken salad (ditch the condiments and dressings) or a piece of fish baked/broiled with some steamed vegetables. Ask to have any sauces/condiments put on the side.

Stock your desk
Not enough time for a meal at work ? Keep a couple of pre-made protein shakes (a couple scoops of protein powder, some grinded oat powder) in plastic shaker bottles at your desk or in your toolbox. In less than thirty seconds, you can add water and consume this meal.

Be Prepared
Keep your car and workstation stocked with tuna pouches/cans, sleeves of rice cakes, bottled water, dry protein powder in shaker bottles, or canisters of nuts (almonds, walnuts, cashew). Cashew is actually a seed from the fruit called cashew apple ! The next time you have to work late or stuck somewhere without a meal, you'll be prepared !