Well, ingredients in the coffee (e.g. sugar) might not reduce acne, but worsening it. Apart from this, if caffeine is keeping you awake, that could be why some individuals may be experiencing higher levels of acne. When you do not have enough sleep, your body is put under much higher levels of stress. When your stress level is increased it will stimulate your hormonal glands that are responsible for androgens(wiki).
Androgen hormones are linked with overproduction of the skin cells, leading to blocked pores. When pores become blocked, the oil and dirt trapped inside can lead to infection and irritation of the blocked pores, causing larger pimples, and a general increase in acne breakouts.
The good news is that there is no proven direct correlation between caffeine intake and acne. However, remember caffeine might cause stress, and stress might cause acne.
So coffee, is not likely to reduce acne.
Caffeine may slightly boost weight loss or prevent weight gain, but there's no sound evidence that increased caffeine consumption results in significant or permanent weight loss.
Although research about the connection between caffeine and weight isn't definitive, there are a few theories about how caffeine might affect weight, including:
1. Appetite suppression. Caffeine may reduce your desire to eat for a brief time, but there's not enough evidence to show that long-term consumption aids weight loss.
2. Calorie burning. Caffeine may stimulate thermogenesis — one way your body generates heat and energy from digesting food. But this probably isn't enough to produce significant weight loss.
Hope this helped you ;)