One of the best ways to write a topic sentence is to use the question or prompt as your guide. Take the key words from the prompt and incorporate them into the topic sentence. Since I don't know the exact prompt, the words "healthy food" are in your original question and should be included. Another great thing to include in your topic sentence is to make sure it answers the questions how or why. For example,
Eating healthy foods is important because it helps maintain a good body weight and fight off diseases. The highlighted "because" phrase tells the reader "why". By including a how or why statement, it tells the reader exactly what you will be writing about in the paragraph. This also works well for thesis statements in essays.
Healthy food is necessary for an athlete because it gives him the energy he needs to perform on the field.
A good topic sentence should specify exactly what you are trying to say about healthy food. For example, if your paper is on healthy food leading to a longer life, your topic sentence would be:
Healthy food can lead to longer lifespans for humans.
It really depends on what you are writing about.
Healthy food can change a person's life for the better.
Eating healthy food is the way to a healthy lifestyle.
A healthy lifestyle is connected to eating healthy food.
Eating healthy food is the key to a healthy lifestyle.
Eating healthy food has proved to increase one's health tremendously.
A good topic sentence should relate the contents of your paragraph. For example: Eating healthy food has many positive benefits. The most important thing to consider when writing topic sentences is to make sure that you convey the broad topic of the paragraph that you are writing.
A topic sentence can be placed anywhere in a paragraph, but it is typically found at the beginning or end of the paragraph. An example of a topic sentence might be "Including healthy foods in our diets can contribute to us living healthier lives," or "We can live healthier lives by eating healthy foods from the six food groups."
A topic sentence contains the main idea of that particular paragraph in which it is included and states the purpose of the writer. Since the topic sentence states the main idea of the paragraph it is usually surrounded by supporting details which elaborate and add meat to the main idea. This is typically done by supporting sentences through the use of examples, illustrations, anecdotes, facts, quotes and figures or numbers.