Vegetables with High Water Content and Low Energy Density

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Explore factual information about the water percentage, energy density, and structural characteristics of everyday vegetables. This resource presents data-driven insights into nutritional composition without medical recommendations or dietary advice.

Assorted fresh vegetables including cucumber, celery, lettuce, and broccoli

Understanding Energy Density in Vegetables

Energy density refers to the amount of calories contained in a given weight of food, typically measured as kilocalories per 100 grams. This concept helps explain why different vegetables vary significantly in their energy content despite similar portion sizes. Understanding water and fibre content provides context for this variation.

Information Notice: The content presented on this page is educational in nature and describes general knowledge about food composition. It is not a substitute for professional dietary or medical advice. Individual nutritional needs vary, and decisions about food consumption should be made independently or in consultation with appropriate professionals.

Key Factors Contributing to Low Energy Density

Several interconnected factors determine why certain vegetables have low energy density values.

High Water Content

Many vegetables consist of 80–95% water by weight. Water contains zero calories, meaning vegetables with exceptionally high water percentages naturally have lower overall energy density regardless of their other components.

Low Fat and Protein Levels

Vegetables are typically low in fat and protein compared to other food groups. Fat provides 9 kilocalories per gram, while protein and carbohydrates provide 4 kilocalories per gram. The minimal fat content in most vegetables contributes significantly to their low overall energy values.

Fibre and Cellular Structure

Many low-density vegetables contain substantial amounts of dietary fibre, which adds weight without significant caloric contribution. The cellular structure—how water, air, and solids are arranged—also influences the perceived fullness and satiety characteristics of vegetables when consumed.

Cross-sections of cucumber, celery, lettuce, and zucchini showing high water content

Leafy Greens Category Overview

Leafy greens represent one of the lowest energy density categories among commonly available vegetables. Their structure and composition create distinctive characteristics worth examining.

Spinach

Water Content: ~91%

Energy Density: ~23 kcal/100g

Fibre Content: ~2.7g/100g

Raw spinach leaves contain substantial water and minimal fat. The cellular structure creates surface area that contributes to perceived volume.

Lettuce (Iceberg)

Water Content: ~96%

Energy Density: ~15 kcal/100g

Fibre Content: ~0.6g/100g

Among the lowest energy density vegetables. The crisp, cellular structure contains mostly water with minimal solids.

Kale

Water Content: ~84%

Energy Density: ~49 kcal/100g

Fibre Content: ~3.6g/100g

Kale contains higher fibre and slightly more protein than other leafy greens, yet remains in the low energy density range.

Fresh spinach, kale, and chard leaves arranged naturally

Cruciferous Vegetables

The cruciferous family (Brassicaceae) includes vegetables known for their distinctive structure and nutritional profiles. Their cellular arrangement and water content contribute to their position among lower-density options.

Broccoli

Water Content: ~89%

Energy Density: ~34 kcal/100g

Fibre Content: ~2.4g/100g

Raw broccoli florets consist primarily of water with cellular cavities. The dense floral structure creates high surface area per unit weight.

Cauliflower

Water Content: ~92%

Energy Density: ~25 kcal/100g

Fibre Content: ~2.4g/100g

Cauliflower shares structural similarities with broccoli but contains slightly more water and less protein, resulting in marginally lower energy density.

Cabbage

Water Content: ~92%

Energy Density: ~25 kcal/100g

Fibre Content: ~2.4g/100g

The layered structure of cabbage contains substantial water between cellular layers. Different varieties (green, red, napa) show minor variations in composition.

Whole broccoli, cauliflower heads, and cabbage wedge showing structural detail

Cucumbers, Celery & Courgettes

These vegetables represent the extreme end of the high-water, low-density spectrum. Their structural characteristics create distinctive textural and compositional profiles.

Cucumber

Water Content: ~96%

Energy Density: ~16 kcal/100g

Fibre Content: ~0.5g/100g

Among the lowest energy density vegetables. The seed cavity and surrounding cellular structure are predominantly water, with thin-walled cells creating a crisp texture.

Celery

Water Content: ~95%

Energy Density: ~16 kcal/100g

Fibre Content: ~0.7g/100g

Celery's distinctive structure comprises water-filled cells separated by fibrous strands. The rigid cell walls provide structural resistance even when raw.

Courgette (Zucchini)

Water Content: ~95%

Energy Density: ~17 kcal/100g

Fibre Content: ~1.1g/100g

Raw courgettes contain extensive water within a thin-walled cellular matrix. The seeds and flesh are approximately 95% water by composition.

Fresh cucumber sliced lengthwise, celery bunch with leaves, and courgette cross-section

Root & Other Low-Density Vegetables

Beyond leafy greens and cruciferous vegetables, other produce items also feature relatively low energy density due to similar compositional factors.

Vegetable	Water Content	Energy Density	Fibre Content
Radish	~95%	~16 kcal/100g	~0.7g/100g
Tomato	~95%	~18 kcal/100g	~1.2g/100g
Bell Pepper	~92%	~31 kcal/100g	~1.9g/100g
Mushroom (Button)	~92%	~22 kcal/100g	~0.7g/100g
Asparagus	~93%	~20 kcal/100g	~2.1g/100g
Pak Choi	~95%	~13 kcal/100g	~1.5g/100g

Approximate nutritional composition values based on observational food composition databases. Individual samples may vary.

Comparison Table of Common Vegetables

Comprehensive reference data for frequently encountered vegetables, organized by energy density.

Vegetable	Water %	kcal/100g	Fibre g/100g	Category
Lettuce (Iceberg)	96%	15	0.6	Leafy Green
Cucumber	96%	16	0.5	High-Water
Celery	95%	16	0.7	High-Water
Radish	95%	16	0.7	Root
Pak Choi	95%	13	1.5	Leafy Green
Tomato	95%	18	1.2	Fruit
Courgette	95%	17	1.1	High-Water
Asparagus	93%	20	2.1	Stalk
Mushroom	92%	22	0.7	Fungus
Bell Pepper	92%	31	1.9	Fruit
Cauliflower	92%	25	2.4	Cruciferous
Cabbage	92%	25	2.4	Cruciferous
Spinach	91%	23	2.7	Leafy Green
Broccoli	89%	34	2.4	Cruciferous
Kale	84%	49	3.6	Leafy Green

Frequently Asked Questions

What does energy density mean? ▼

Energy density is a measurement of calories per unit weight, typically expressed as kilocalories per 100 grams. It describes how much energy (calories) is concentrated in a given amount of food. Lower energy density means fewer calories per 100 grams; higher energy density means more calories per 100 grams. This concept helps explain why similar portion weights of different foods may contain very different calorie amounts.

Why do vegetables have such high water content? ▼

Vegetables are living organisms that require water for physiological processes including nutrient transport, cellular rigidity, and photosynthesis. Water maintains cellular turgor pressure, which keeps plants firm and upright. Additionally, water is essential for maintaining cellular function. This structural and biological necessity results in most vegetables being 80–96% water by weight, with only the remaining solids (carbohydrates, proteins, minerals, fibre) contributing measurable calories.

How is fibre content measured, and what role does it play? ▼

Dietary fibre is typically measured in grams per 100 grams of food and refers to carbohydrate compounds that are not digestible by human enzymes. Fibre provides structural integrity to vegetables and contributes to their bulk and texture. While technically a carbohydrate, most fibre sources contribute minimal calories because they pass through the digestive system largely unabsorbed. Vegetables with higher fibre content also tend to have more pronounced cellular structure and volume characteristics.

Are all low-energy-density vegetables nutritionally similar? ▼

Although low-energy-density vegetables share similar calorie values per 100 grams, they differ substantially in micronutrient content, phytonutrient profiles, and macronutrient distributions. For example, spinach contains more iron and protein than lettuce, while cruciferous vegetables contain specific compounds absent in other families. Diversity in vegetable consumption ensures exposure to a broader range of micronutrients and bioactive compounds.

How does cooking affect energy density? ▼

Cooking causes water loss from vegetables, which concentrates the remaining solids and increases energy density per unit weight. For example, cooked broccoli contains more calories per 100 grams than raw broccoli due to reduced water content. However, total calorie intake depends on the actual amount consumed. Cooking methods also affect nutrient bioavailability—some nutrients become more available when heated, while others may be reduced depending on temperature and duration.

What determines the crispness and texture of vegetables? ▼

Crispness in vegetables derives from rigid cell walls and cellular turgor pressure—maintained by water content. Vegetables like celery and cucumber possess strong cell walls composed of cellulose and pectin that resist breakage. The water pressure inside cells (turgor) keeps these walls rigid and creates the characteristic crisp texture when fresh. As vegetables age or lose water, turgor pressure decreases, resulting in wilting or reduced crispness.