How to get a crispy finish in the oven and reduce calories: techniques and tips

Why does frying add so many calories?

When you submerge food in hot oil, the water on its surface evaporates rapidly. This leaves tiny gaps that the oil fills, which is why fried food contains much more fat than it did raw.

The Spanish Food Composition Database shows this with potatoes. Raw potatoes provide fewer than 90 kcal per 100 g, while home-fried potatoes contain around 290 kcal [1]. That is more than three times the energy in the same portion.

This does not mean you have to avoid fried food altogether. If you use olive oil and do not reuse it, fried food can fit into any eating plan from time to time. When you want to lose weight, what matters is how often you eat it, and the oven can make a real difference.

What does “frying” in the oven mean?

It means cooking with high, dry heat, at around 200 °C, to dry the surface of the food quickly. This creates a golden crust similar to one from frying, with very little added fat.

Instead of submerging the food, coat it with a thin film of oil using a spray bottle or a pastry brush. One teaspoon, about 5 g of extra virgin olive oil, provides around 45 kcal and is enough to coat a portion of potatoes [1].

The Spanish obesity guideline recommends a moderate energy deficit for weight loss, one that can be maintained over time [2]. Cooking changes like this can help you achieve that without giving up the dishes you enjoy.

Temperature and cooking time for different foods

Always preheat the oven, using conventional heat or the fan setting, and do not overcrowd the tray. Cooking times are a guide, as ovens vary. Use the colour as your cue.

• Chips or potato wedges. At 200 °C, cook for 25 to 35 minutes, turning them halfway through.
• Homemade or chilled croquettes. At 200 °C, cook for 15 to 20 minutes, turning them gently halfway through.
• Small savoury pastries. At 190 or 200 °C, cook for 12 to 15 minutes, until the pastry turns golden.
• Breaded fish or chicken. At 200 °C, cook thin pieces for 15 to 18 minutes.
• Baked eggs with vegetables. At 180 °C, cook for 10 to 12 minutes, just long enough for the white to set while the yolk stays soft.

How do you make oven-baked potatoes that taste like chips?

These are the steps we share in consultations with anyone who says they cannot get through the week without chips.

1. Cut the potatoes into evenly sized thick chips, about one centimetre wide. They turn out better than thin slices.
2. Rinse them well in cold water or soak them for 20 to 30 minutes. This removes surface starch, which would make them sticky, and reduces acrylamide formation during cooking [3].
3. Drain them and dry them thoroughly with a clean tea towel or kitchen paper. Moisture is what most often stops them becoming crisp.
4. Put them in a bowl with a teaspoon of extra virgin olive oil, paprika, garlic powder and black pepper. Mix by hand so they are all coated.
5. Spread them out on baking parchment in a single layer, with space between each piece. Bake at 200 °C for around 25 to 35 minutes, turning them halfway through.

If you use frozen chips, they already have a thin layer of oil added during manufacture. Do not add more. Spread them on the tray and bake at the temperature on the packet until golden.

Other dishes that work well in the oven

You can cook almost any dish that would usually go in a frying pan on a baking tray instead.

Croquettes. Place them well chilled on baking parchment and spray a little oil over them. The breadcrumbs turn golden without cracking, and they only contain that oil, rather than the oil they absorb when fried.

Small savoury pastries. Cook the filling in a pan with a little oil, seal the edges with a fork and brush the pastry with beaten egg or a tablespoon of semi-skimmed milk. They turn out glossy and crisp.

Breaded fish. Dip fillets of hake, cod or sea bream in beaten egg, then coat them in wholemeal breadcrumbs mixed with a tablespoon of crushed oats. A quick bake at 200 °C keeps them juicy without soaking them in oil.

Baked eggs. Put a layer of homemade blended tomato and vegetables in a small ovenproof dish, make a well and crack an egg into it. At 180 °C, you get the same protein without the oil absorbed by a fried egg.

What mistakes do we see in consultations?

The technique is simple, but three common pitfalls come up again and again.

• Pouring the oil straight from the bottle. “It is olive oil, so it does not matter.” It is a good-quality fat, but each teaspoon still adds 45 kcal [1]. A spray bottle or pastry brush uses much less.
• Wet or overcrowded potatoes. They come out soft, leading people to conclude that oven-baked potatoes do not work. Almost always, they needed drying or more space on the tray.
• Assuming everything cooked in the oven is light. Many ready-made breaded foods are already part-fried in the factory. Check the fat per 100 g on the label before counting them as oven-baked.

Get them golden, not burnt

When cooked above 120 °C with little moisture, potatoes, bread and other starchy foods form acrylamide [4]. It is produced by a reaction between an amino acid, asparagine, and the food’s own sugars.

The European Food Safety Authority (EFSA) concluded that acrylamide in food may increase the risk of cancer in people of all ages [4]. That is why it is best to take potatoes out as soon as they are golden, before they darken, and discard any burnt parts [3]. Do not store raw potatoes in the fridge, as the cold increases their sugar levels [3]. If you do fry them, keep the oil below 175 °C [3].

If you are losing weight

Each time you swap a portion of chips for oven-baked potatoes, that side dish provides less than half the energy [1]. Having them two or three times a week is a small change that can make a difference without giving up a dish you enjoy.

To reduce the energy in your other dishes, see how to reduce calories without going hungry. If you cook for several days, organising lunch boxes and batch cooking may help. The full overview is in our weight-loss guide.