Those people who are eating fast food regularly are more like to get high cholesterol, blood pressure, sugar and several other diseases so it is evident that fast food is unhealthy.
This sentence is a bit awkward and needs rewording. In the introduction of an IELTs essay, you do not have to give reasons to clarify your points. Just describe the issue and state your opinion on it.
Then, it seems to me you didn't give enough reasons as to why you think fast food is unhealthy. What's more, the topic sentence of a paragraph should stand out from the others, which in turns strengthen the point that the topic sentence makes. In the second paragraph, for example, the reader can hardly figure out what point you are going to make until they read the third sentence. This is I think not good for an IELTs essay.