put on weight表示“发福，增加体重”。
If you eat too much, you will put on weight very easily.
I can eat what I want but I never put on weight.
我能想吃什么就吃什么，但是体重从来不增加。
I've put on a little weight.
我长胖了点。
I'm forever on a diet, since I put on weight easily.
我永远都在减肥，因为我很容易长胖。
You have put on weight.
你发福了。
He's put on weight.
他胖了。
Lack of sleep can also make you put on weight.
睡眠不足还会使人长胖
I hope you're not trying to plump me up.
我希望你不要试图把我养胖。
类似说法：
Oh, I gained some weight.
天啊，我长胖了。
I have gone up a size.
我胖了一个码。
A girl told me donating blood would make her gain weight. Not true.
有位姑娘告诉我，献血会使她的体重增加，这不正确。
The reason I put on weight was poor eating habits. I am trying to eat better and exercise more. This is my goal.
我增肥的原因就是糟糕的饮食习惯。 我正尽可能去吃得好些，加强锻炼。这是我的目标。
In winter，I gain weight so easily even I stop eating meat.
在冬天，尽管我不吃肉，我也很容易长胖。
I have put on some weight during the holiday.
我假期长胖了。
lose/reduce weight减肥
It makes sense to eat a reasonably balanced diet when slimming.
在减肥过程中保持饮食的营养相对均衡是明智的。
on a diet节食；控制饮食；减肥
count/burn calories
计算/燃烧卡路里即减肥
No doughnut for me, I am counting/burning my calories.
不要给我吃甜甜圈了，我在减肥（计算/燃烧我的卡路里）。