This study explored the information sources long-distance triathletes used to inform their training and nutrition plans, and evaluated these plans over a training macrocycle. Seventy-four long-distance triathletes completed the online survey. Coaches were the most popular training information source (69%), whereas nonprofessional sources (internet 65%, other athletes 53%) were more popular than nutritionists (29%) for nutrition information. Attributes valued most in an information source were: source prior personal experience, individualized advice, breadth of knowledge, and credibility. Sixty-five percent of participants reported previously manipulating dietary intake to improve performance. Forty-three percent reported carbohydrate loading previously, but only 29% planned to carbohydrate load for their upcoming event. Thirty-six percent of participants planned to reduce carbohydrate intake at some point in training, predominantly early (28%) and toward the end (22%) of their macrocycles. Twenty percent of participants planned to maintain energy intake early, and increase (14%) or maintain energy intake (15%) mid-cycle. Triathletes’ training plans showed intentions for concurrent increases in volume and intensity, rather than a classical periodized training progression. Limitations of this study include the lack of diet intake and training data, quantitative comparison with dietary guidelines and high/low carbohydrate classification, and an overrepresentation of women in the study cohort. This research showed the popularity of the internet and other athletes to inform triathletes’ nutrition plans, and revealed intentions to reduce carbohydrate intakes alongside training load increases, contrary to professional guidelines. Understanding athletes’ intentions and sources of nutrition information is crucial to developing effective nutrition education strategies.