Plant-Based & Vegan Diets vs Volumetrics
A side-by-side comparison — no verdict on which is "better," just how they differ.
Plant-Based & Vegan Diets
Related but distinct patterns built around minimizing (plant-based) or fully excluding (vegan) animal products, centering whole plant foods like fruits, vegetables, legumes, whole grains, nuts, and seeds.
View full Plant-Based & Vegan Diets page →Volumetrics
Organizes eating around a food’s energy density (calories per gram) rather than restricting any food group — building meals around lower-density, water- and fiber-rich foods to feel full on fewer calories.
View full Volumetrics page →Key Differences
- On animal foods they sit far apart: Plant-Based minimizes or fully excludes animal products, whereas Volumetrics includes animal foods such as fish, poultry, eggs, or dairy.
- They differ a lot in strictness. Volumetrics sets few hard rules and bans nothing outright, while Plant-Based cuts out or sharply limits whole food groups.
- One works on calories and one doesn't. Volumetrics lowers calories by favoring foods with fewer calories per bite, and Plant-Based leaves calories alone.
What They Share
Both build meals around vegetables, fruit, whole grains, and beans and lentils.
Typical Foods
Plant-Based & Vegan DietsLegumes, tofu, tempeh, seitan, whole grains, nuts and seeds; the vegan version fully excludes meat, poultry, seafood, dairy, eggs, and honey.
VolumetricsVery-low-density: broth-based soups, non-starchy vegetables, most fruit. Low-density: starchy vegetables, whole grains, legumes, low-fat dairy, lean protein — the everyday staples.
Foods to Avoid
Plant-Based & Vegan DietsVegan: all animal-derived foods and ingredients. Plant-based (looser): minimizes but doesn’t require full exclusion of meat, dairy, or eggs.
VolumetricsNone eliminated — higher-density foods (nuts, seeds, dried fruit, oils and butter, chips, chocolate, cookies) are enjoyed in smaller amounts, not banned.
Eating Pattern
Plant-Based & Vegan DietsNo specific eating window.
VolumetricsNo specific eating window — organized around food energy density, not timing.
Primary Goal
Plant-Based & Vegan DietsCardiometabolic health, often alongside environmental or ethical motivations.
VolumetricsWeight loss via increased fullness/satiety per calorie.
Best For
Plant-Based & Vegan DietsPeople motivated by environmental or ethical concerns, or by the cardiometabolic risk reduction the research points to, who are willing to plan meals rather than eat on autopilot.
VolumetricsPeople who find restriction-based dieting hard to sustain because they end up hungry, and who like understanding the “why” behind a recommendation.
Macro Emphasis
Plant-Based & Vegan DietsNone specified — food-group based, not macro-ratio based.
VolumetricsNone — organized around energy density (calories per gram), not macro ratios.
Health Condition Relevance
Plant-Based & Vegan DietsLower BMI, lower rates of type 2 diabetes and heart disease, and lower all-cause mortality in large cohort studies — concentrated in “healthful” plant-based patterns, not ones built on refined carbs and sugar.
VolumetricsNot tied to a specific health condition — a general weight-loss/satiety focus.
Evidence Strength
Plant-Based & Vegan DietsStrong cohort evidence (e.g. Adventist Health Study-2, ~73,000 people) though observational rather than randomized for the core mortality/disease claims.
VolumetricsModerate. A decades-long Penn State research program (Dr. Barbara Rolls) shows lower energy density reduces calorie intake, and a year-long trial in 97 women found adding fruit and vegetables to a reduced-fat diet led to more weight loss and less hunger. A 2022 meta-analysis found no significant weight effect, and long-term results are inconsistent.
Restrictiveness
Plant-Based & Vegan DietsVariable — plant-based is low restrictiveness (a spectrum, no full exclusion); vegan is high (full animal-product exclusion).
VolumetricsLow — no foods eliminated, just density-tier awareness; requires some ongoing attention to food composition rather than fixed rules.
Cost / Accessibility
Plant-Based & Vegan DietsGenerally less expensive overall than a meat- and dairy-centered diet, since savings from cutting meat and dairy tend to outweigh the added cost of vegetables, whole grains, and plant-based meat substitutes, though reliable access to fresh produce remains a real barrier in areas with limited grocery options.
VolumetricsBuilt on inexpensive, widely available staples (produce, whole grains, legumes, broth-based soups, lean protein) with no specialty products required, making it one of the more budget-friendly structured approaches.
Nutrients to Watch
Plant-Based & Vegan DietsVitamin B12 is the main one for vegans, and it needs fortified foods or a supplement. Iodine, calcium, zinc, selenium, vitamin D, and omega-3s also need planning. Planned well, vegan diets can meet adult nutrient needs.
VolumetricsNo gaps are documented. Low-energy-density diets are linked with higher intake of vitamins A, C, and B6, folate, iron, calcium, and potassium.
Adjustment Period
Plant-Based & Vegan DietsMore beans often means more gas at first, though fewer than half of people report it in the first week. No adjustment timeline has been studied.
VolumetricsLittle is known. In its main year-long trial, the group eating more fruit and vegetables reported less hunger, not more.
A Sample Day
Plant-Based & Vegan DietsBreakfast: oatmeal made with fortified soy milk, ground flax, and berries. Lunch: chickpea and quinoa salad with vegetables, tahini, and pumpkin seeds. Dinner: tofu or tempeh stir-fry with broccoli over brown rice. Snack: hummus with carrots. Plus a B12 supplement or fortified foods.
VolumetricsBreakfast: oatmeal with berries and a hard-boiled egg. Lunch: broth-based vegetable soup, then a turkey sandwich on whole-grain bread with lettuce and tomato. Dinner: big green salad, grilled fish, brown rice, and roasted vegetables. Snack: grapes with nonfat Greek yogurt.
Prep and Eating Out
Plant-Based & Vegan DietsModerate prep, with planning for protein variety and fortified foods. Plant-based eating is easy at restaurants. Strict vegan eating is harder, since animal ingredients hide in many dishes.
VolumetricsLow to moderate prep, since soups and salads can be made in batches and nothing is tracked. Easy to eat out: start with a broth-based soup or salad and fill up on vegetables.
Talk to a Clinician First If
Plant-Based & Vegan DietsChildren on vegan diets need careful planning, since studies show shorter height and lower iron and B12 status. Pregnant and breastfeeding people need a reliable B12 source and should ask about omega-3s. One large study found higher hip fracture risk in vegans. Warfarin users should keep leafy-green intake steady.
VolumetricsNot studied. No specific cautions have been published for Volumetrics.
Sticking With It and Stopping
Plant-Based & Vegan DietsIn a six-month trial, people stuck with a vegan diet about as well as with other diets, and the vegan group lost the most weight. In a 74-week trial in type 2 diabetes, weight loss held up as well as on a standard diabetes diet. No trial has tracked what happens after people stop.
VolumetricsIn its year-long trial, about 73% of participants finished. In a small seven-month trial, a low-energy-density diet reduced weight regain after weight loss. Over the long term, lower-density diets have not consistently produced more weight loss than calorie restriction alone.
Educational only, not medical advice. Want to compare a different pair? Back to Diet Arena.