Many people who decide to resume eating meat do so simply because they wanted to satisfy their psychological cravings and fall back to old habits; they use health as a justification to save face in public. There are healthy and unhealthy vegans, just as there are healthy and unhealthy omnivores. Studies have shown that vegans who eat varied low-fat foods stand a much better chance of living longer, healthier lives than their meat and dairy-eating counterparts.
Some people who adopt a vegan diet experience symptoms of their body finally ridding itself of the all the toxins that have been built up from ingesting meat and dairy, and this can be temporarily uncomfortable. Like meat and dairy eaters, vegans who eat too much processed food, fatty food, and sugary food may find their health suffers and their energy decreases.
However, there is no shortage of vegan health and nutrition resources available for those who are willing to seek them out. For those who have concerns about their nutritional requirements, there are vegan Registered Dietitians that have compiled recommendations. Two excellent sources of comprehensive nutritional information for vegans are Vegan Health and Vegan RD.