Lifestyle medicine and, in particular, medical nutrition therapy (MNT) is the cornerstone of gestational diabetes mellitus (GDM) management. MNT aims to achieve normoglycemia, prevent ketosis, provide adequate gestational weight gain, and optimize fetal growth. Evidence-based MNT can negate pregnancy complications, improve obstetrical outcomes, and reduce the risk for maternal and fetal adverse events. Although achieving an energy equilibrium is vital for improving all outcomes, specific daily energy intake goals are rarely suggested in clinical practice guidelines. Moreover, despite the plethora of dietary supplements tested in randomized controlled trials in women with GDM, very few have demonstrated beneficial effects in maternal-fetal outcomes. An energy-prudent and nutritionally adequate diet comprises the core of all successful nutrition interventions.