One tablespoon of olive oil is 119 calories (500 kJ). A whole cup of sliced zucchini is 18 calories (76 kJ). Both are food, and healthy food at that. The difference between them is not virtue…it’s water.
Almost every article about high-volume, low-calorie foods names energy density as paramount without breaking that advice down by the numbers. And they’re right to do that—up to a point. Your body needs protein to function. How you stay full when you’ve had enough protein is what we’re talking about here.
Energy density refers to calories or kilojoules per gram. Zucchini is 0.16 calories per gram (0.67 kJ per gram). Olive oil is 8.84 (37.1). That is roughly a 55-fold difference by weight.
Energy density isn’t a simple equation for everyone, though, and if you’re on semaglutide or tirzepatide, the ranking below may even work against you. Appetite is already small on a GLP-1, so the best snacks on Ozempic or a similar medicine fall on the heavy end of this table, where the protein is.
Below are 19 foods, each measured by a standard household portion, its gram weight, and its calories per gram. Use this guide to help you structure your meals and snacking throughout the day, so you can get just enough protein and fill up on low-calorie, high-water foods between.
19 Foods Sorted by Calories Per Gram
This guide is sorted lightest to densest. The first four foods are the ones you can eat a genuinely large amount of, whereas the last require smaller portions.
| Food | Typical portion | Energy per portion | Per 100 g | Calories per gram (kJ per gram) |
|---|---|---|---|---|
| Celery, raw | 1 cup chopped (100 g) | 14 calories (59 kJ) | 14 calories (59 kJ) | 0.14 (0.59) |
| Cucumber, raw with peel | 1/2 cup slices (52 g) | 8 calories (34 kJ) | 15 calories (63 kJ) | 0.15 (0.63) |
| Zucchini, raw | 1 cup sliced (112 g) | 18 calories (76 kJ) | 16 calories (67 kJ) | 0.16 (0.67) |
| Romaine lettuce, raw | 1 cup shredded (47 g) | 8 calories (34 kJ) | 17 calories (71 kJ) | 0.17 (0.71) |
| Cauliflower, raw | 1 cup (100 g) | 25 calories (105 kJ) | 25 calories (105 kJ) | 0.25 (1.05) |
| Watermelon, raw | 1 cup diced (152 g) | 46 calories (193 kJ) | 30 calories (126 kJ) | 0.30 (1.26) |
| Strawberries, raw | 1 cup whole (144 g) | 46 calories (193 kJ) | 32 calories (134 kJ) | 0.32 (1.34) |
| Broccoli, boiled and drained | 1/2 cup chopped (77 g) | 27 calories (113 kJ) | 35 calories (147 kJ) | 0.35 (1.47) |
| Carrots, raw | 1 medium (61 g) | 25 calories (105 kJ) | 41 calories (172 kJ) | 0.41 (1.72) |
| Greek yogurt, plain nonfat | 1 cup (about 240 g) | 132 calories (554 kJ) | 55 calories (231 kJ) | 0.55 (2.31) |
| Blueberries, raw | 1 cup (148 g) | 83 calories (349 kJ) | 57 calories (239 kJ) | 0.57 (2.39) |
| Oats, cooked with water | 1 cup cooked (234 g) | 147 calories (617 kJ) | 63 calories (265 kJ) | 0.63 (2.65) |
| Cottage cheese, 1% milkfat | 4 oz (113 g) | 81 calories (340 kJ) | 72 calories (302 kJ) | 0.72 (3.02) |
| Cod, Atlantic, cooked dry heat | 3 oz (85 g) | 89 calories (374 kJ) | 105 calories (441 kJ) | 1.05 (4.41) |
| Egg, large, whole | 1 large (50 g) | 74 calories (311 kJ) | 147 calories (617 kJ) | 1.47 (6.17) |
| Popcorn, air-popped | 1 cup (8 g) | 31 calories (130 kJ) | 387 calories (1,625 kJ) | 3.87 (16.3) |
| Cheddar cheese | 1 oz / 1 slice (28 g) | 114 calories (479 kJ) | 403 calories (1,693 kJ) | 4.03 (16.9) |
| Almonds, raw | 1 oz, about 23 kernels (28 g) | 164 calories (689 kJ) | 578 calories (2,428 kJ) | 5.78 (24.3) |
| Olive oil | 1 tablespoon (13.5 g) | 119 calories (500 kJ) | 884 calories (3,713 kJ) | 8.84 (37.1) |
Figures are estimates based on USDA composition data (SR Legacy) via FoodData Central-derived listings, part of the food energy reference. Actual weights and calories may vary.
Why Eating More Food for Fewer Calories Actually Works
Your stomach cannot count. What it can do is stretch.
Fullness is signaled largely by mechanical stretch of the stomach wall, picked up by mechanoreceptors on vagal nerves and relayed to the brainstem. Steinert, Meyer-Gerspach, and Beglinger called that signal volumetric (American Journal of Physiology-Endocrinology and Metabolism, 2012): It tracks how far the wall is distended, largely independent of the calories doing it. Stretch, as one input among several that signal hunger, can help a big plate of light food feel like a small plate of a dense one.
That might seem counterintuitive on the surface, but that’s why water-rich food is key here. Barbara Rolls at Penn State originated the energy-density framing. According to her research, lowering a diet’s energy density, mostly by adding water-rich foods, leads people to spontaneously eat less without feeling restricted (Physiology and Behavior, 2009). A glass of water drunk simultaneously with the meal did not achieve the same results.
Ello-Martin and colleagues then ran a year-long randomized trial (American Journal of Clinical Nutrition, 2007).
One group was told to cut fat, the other to cut fat and add fruit and vegetables. At one year the second group had lost 7.9 kg against the first’s 6.4 kg while eating about 225 g more food per day by weight, as well as reporting less hunger throughout. The gap was modest, about 1.5 kg over a year, but it came from a controlled trial rather than a correlation.
What separated the groups was energy density. The second group consumed an average of 1.23 calories per gram (5.17 kJ per gram), whereas the first had consumed an average of 1.46 (6.13 kJ per gram). By eating more foods with less energy density, the second group felt fuller longer and lost more weight.
The Best Snacks on Ozempic
Volume eating doesn’t necessarily translate to a GLP-1 diet. The idea above is to fill up on foods that weigh a lot (from water) with fewer calories.
Semaglutide and tirzepatide already make you feel full by slowing digestion, so a large plate of high-water vegetables can sit heavily. The medications effect makes portion size stop mattering as much because you simply stop eating before it becomes an issue. That’s what people mean when they say “food noise” quietens on a GLP-1.
The food guide below isn’t useless to GLP-1 patients, of course. You just need to flip the order. Protein first, volume second. The Greek yogurt, cottage cheese, eggs, and fish near the top of the table are worth keeping when appetite is small because a limited number of bites should carry as much protein as possible. Save the celery and cucumber for when you want something to chew rather than something to count on to fuel your day.
1. Water Is Doing Almost All the Work: Celery, Cucumber, Zucchini, Romaine, and Watermelon
Four cups of shredded romaine contain 32 calories (134 kJ). That is a full mixing bowl of salad for less than half the calories an egg.
These five sit between 0.14 and 0.30 calories per gram, and they get there the same way. All weights are approximate.
Celery: 0.14 calories per gram
- Medium stalk, 40 g, 6 calories (25 kJ)
- Large, 11–12 inches, 64 g, 9 calories (38 kJ)
Cucumber with peel: 0.15 calories per gram
- Whole, 8 1/4 inches, 300 g, 45 calories (189 kJ)
- Less than a slice of bread
Zucchini: 0.16 calories per gram
- One medium, 194 g, 31 calories (130 kJ)
Romaine: 0.17 calories per gram
- Almost entirely water
- Whole head, 624 g, 106 calories (445 kJ)
Watermelon: 0.30 calories per gram
- 91% water
- One cup diced, 152 g, 46 calories (193 kJ)
- A wedge of about 1/16 of a melon, 286 g, 86 calories (361 kJ)
You can snack on these foods alone or with your meals and protein. They should not form the basis of a meal, though, because they don’t contain meaningful protein or fat.
2. Fiber and Structure: Cauliflower, Broccoli, Carrots, Strawberries, and Blueberries
Blueberries are almost four times as dense as cucumber. One cup of them is 83 calories (349 kJ), nearly two whole cucumbers. That is not an argument against blueberries. It is an argument for knowing the number.
This group of foods weighs about 0.25 to 0.57 calories per gram. They are still water-rich but contain more fiber and, in the fruit, more sugar.
Cauliflower: 0.25 calories per gram
- One cup, 100 g, 25 calories (105 kJ)
Broccoli, boiled and drained: 0.35 calories per gram
- Half a cup chopped, 77 g, 27 calories (113 kJ)
- One 5-inch spear, 37 g, 13 calories (55 kJ)
Carrots: 0.41 calories per gram
- Densest vegetable on this list
- One medium, 61 g, 25 calories (105 kJ)
Strawberries: 0.32 calories per gram
- One cup whole, 144 g, 46 calories (193 kJ)
- One cup sliced, 166 g, 53 calories (223 kJ)
Blueberries: 0.57 calories per gram
- One cup, 74 g, 83 calories (176 kJ)
The sugar in fruit explains why berries are denser than vegetables. Fiber helps stomachs feel full longer, so you’ll find that tough, fiber-rich foods like broccoli and cauliflower also qualify as higher-density than some other vegetables.
One cup of blueberries at 83 calories against one cup of shredded romaine’s 8 calories (34 kJ) represents a ten-to-one ratio even though both are fresh produce measured at the same volume. For everyday foods more broadly, see typical foods and their energy.
3. The Protein Foods: Greek Yogurt, Cottage Cheese, Eggs, and Cod
Read the table as a ranking and an egg looks like a mistake. It is 1.47 calories per gram, 10 times denser than cucumber, and it is 74 calories (311 kJ). None of the food on the table above is a mistake. The table is not a ranking of good food versus bad. When you need protein, which you do, these are the foods you’ll want on your plate. Here’s where they land in energy density:
Greek yogurt plain and nonfat: 0.55 calories per gram
- One cup, 240 g, 132 calories (554 kJ)
Cottage cheese at 1% milkfat: 0.72 calories per gram
- Four ounces (113 g), 81 calories (340 kJ)
- One cup unpacked 163 calories (685 kJ)
Cod baked or broiled with no added fat: 1.05 calories per gram
- Three ounces (85 g), 89 calories (374 kJ)
- One whole fillet, 180 g, 189 calories (794 kJ)
Eggs: 1.47 calories per gram
- One large egg raw (50 g), 74 calories (311 kJ) on the raw basis
- Cooking in fat adds calories
These four are what turn a large plate into a meal. Past a point, lower calories per gram means lower protein and fat, and you will notice. If your volume plates keep leaving you hungry an hour later, the missing thing is usually in this group, not the vegetable column.
4. When Air and Absorbed Water Do the Work: Popcorn and Oats
Air-popped popcorn is 387 calories (1,625 kJ) per 100 g. Cheddar cheese is 403 calories (1,693 kJ) per 100 g. By weight they are nearly the same food, but popcorn comes out on top with more fiber and less fat.
Air-popped popcorn: 387 calories per 100 g
- One cup, 8 g, 31 calories (130 kJ)
- One ounce, 28 g, 110 calories (462 kJ)
“Calories per gram” describes the food but does not tell you what a real portion weighs. Popcorn is mostly air, so it doesn’t weigh much.
Oats: 389 calories per 100 g
- One cup dry, 80 grams, 607 calories (2,549 kJ)
- One cup cooked with water, 234 g, 147 calories (617 kJ)
Water absorbs during cooking, causing less oats to weigh more, which is why the calories are fewer. This is why you should always weigh or measure a food in the state you eat it in.
5. The Other End of the Spectrum: Cheddar, Almonds, and Olive Oil
A handful of almonds and a big bowl of salad greens can weigh about the same. Twenty-eight grams of almonds weigh 164 calories (689 kJ). Twenty-eight grams of romaine, derived from its 17 calories (71 kJ) per 100 g, is about 5 calories (21 kJ). Same weight in your hand, thirty times the energy.
Cheddar: 4.03 calories per gram
- One slice (28 g), 114 calories (479 kJ),
- One cup shredded (113 g), 455 calories (1,911 kJ)
- About 74% of calories from fat
Almonds: 5.78 calories per gram
- One ounce, 23 nuts (28 g), 164 calories (689 kJ)
- One cup whole (143 g), 827 calories (3,473 kJ)
- Also about 74% from fat
Olive oil: 8.84 calories per gram
- Densest food on this list
- One tablespoon (13.5 g), 119 calories (500 kJ)
- One teaspoon (4.5 g) 40 calories (168 kJ)
All the calories in olive oil come from fat and none of its weight is water.
These are not bad foods. Almonds and olive oil are nutritious. Density and nutrition are not the same, nor are they mutually exclusive. The two work in tandem, and this article measures one.
How Cooking Changes Food Density
There is no general rule that cooking concentrates calories. How cooking affects a specific food depends on what the water does.
Oats move the most, from 389 calories (1,634 kJ) per 100 g dry to 63 calories (265 kJ) per 100 g cooked.
Zucchini barely moves. Raw is 16 calories (67 kJ) per 100 g. Boiled and drained is also 16 calories (67 kJ) in the same source, and a cup of cooked zucchini slices (180 g) is 29 calories (122 kJ). It starts mostly water and ends mostly water, so boiling concentrates almost nothing.
Spinach is the one most people get wrong. Raw and boiled spinach drained both land near 23 calories (97 kJ) per 100 g. The bag-cooks-down-to-two-bites effect is real, but it is about cup volume: raw leaves are light and full of air, wilted leaves pack densely, so a cup of cooked spinach holds far more spinach while its calories per gram barely moved.
One rule holds: Cooking in fat raises the number substantially, and spinach cooked in a generic fat lands near 40 calories (168 kJ) per 100 g. That is a property of the fat, not the vegetable.
Limitations of This Approach
Nobody here is going to tell you how much to eat. This is not a diet. It is a description of how food behaves on one scale, and it runs into three limits.
Protein and fat: Eating mostly water-rich, low-calorie foods can leave both protein and fat short, which most people will want to avoid. Reviewers of the volumetrics approach have pointed out that its categories put nuts and seeds in the same tier as sweets and fast food, and that its recommended protein intake runs modest, roughly 10%–15% of calories. It’s important that you combine volume eating with appropriate intake of protein and healthy, unsaturated fats.
Fiber tolerance: Raising fiber quickly can cause gas, bloating, and gut discomfort. As gut bacteria ferment your stomach’s contents, a microbiome that has not adapted reacts poorly. Increasing your fiber intake should begin gradually, topping off at the general guidance of around 25 to 38 g a day. People with IBS may struggle to add fiber to their diet without exacerbating their symptoms, so consult your gastroenterologist before changing fiber intake.
Low-calorie vs. nutrient-dense: Nutrient density reflects a food’s content of vitamins, minerals, and protein relative to calories; energy density is calories per gram. A food can be low in calories and nutrients (iceberg lettuce), low in calories and high in nutrients (zucchini), or calorie-dense and highly nutritious, which is what almonds and olive oil are.
The goal is to deliberately build balanced meals from low-calorie, nutrient-dense foods. This table helps you know which foods do what as you aim for this energy balance.
FAQ
Does volume eating actually work or is it just a way to feel busy while eating?
Volume eating works for many people, and there is a year-long randomized trial behind it. Ello-Martin and colleagues (American Journal of Clinical Nutrition, 2007) found that participants who cut fat but added fruit and vegetables lost 1.5 kg more than a group cutting fat alone, even though they ate about 225 g more food per day.
Does drinking a glass of water with a meal do the same thing as eating water-rich food?
No, drinking a glass of water with a meal does not do the same thing as eating water-rich food. Water incorporated into a food’s structure can lower energy intake, while water drunk simultaneously with a meal is unlikely to produce the same effect.
Why is air-popped popcorn on a low-calorie list at 387 calories (1,625 kJ) per 100 g?
Popcorn is mostly air, and 100 g of it is more than an average person would eat in one sitting. One cup weighs about 8 g and 31 calories (130 kJ). A large bowl of popcorn is 28 g and 110 calories (462 kJ). So, 100 g of popcorn would be approximately four large bowls. Calories per gram describes the food; it does not tell you what a real portion weighs.
Do these numbers change when the food is cooked?
Sometimes calories per gram change drastically when a food is cooked, sometimes not at all. Oats go from 389 calories (1,634 kJ) per 100 g dry to 63 calories (265 kJ) per 100 g cooked with water. Zucchini is 16 calories (67 kJ) per 100 g either way.
Are low-calorie foods automatically healthy?
No, low-calorie foods are definitely not automatically healthy. Energy density is calories per gram. Nutrient density is vitamins, minerals, and protein relative to calories. A food can be low in both calories and nutrients, low in calories and high in nutrients, or calorie-dense and highly nutritious. It just depends on the food.