Keto Lamb Loin with Garlic and Thyme
This keto lamb loin (also called lamb backstrap) is seared whole, roasted pink in the oven with garlic cloves and thyme sprigs, and rested before slicing. Each serving delivers 54 g of protein and 50 g of fat with just 2 g of net carbs, a holiday roast with no fussy sides, ready in 35 minutes.
Key Takeaways
- Total time: approx. 35 minutes, 5 minutes prep, 6 minutes pan, 18 minutes oven, 5 minutes resting.
- Approx. 2 g net carbs and 50 g fat per serving.
- Ingredients: lamb loin, butter, garlic, fresh thyme, rosemary, olive oil, salt, pepper.
- Works as a keto holiday roast for Sunday or a birthday with minimal side dishes.
Ingredients
One serving equals 250 g of lamb loin with about 15 g of garlic butter, intended as a main course on its own or with a green salad.
| Amount | Ingredient | Note | ||
|---|---|---|---|---|
| lamb loin | whole, trimmed (silverskin removed) | |||
| whole, trimmed (silverskin removed) | ||||
| butter | - | |||
| garlic cloves | lightly crushed with the flat of a knife, not chopped | |||
| lightly crushed with the flat of a knife, not chopped | ||||
| fresh thyme | approx. 4 sprigs | |||
| approx. 4 sprigs | ||||
| fresh rosemary | approx. 1 sprig | |||
| approx. 1 sprig | ||||
| olive oil | approx. 1 tbsp | |||
| approx. 1 tbsp | ||||
| salt | to taste | |||
| to taste | ||||
| pepper | to taste | |||
| to taste | ||||
Preparation
Pat the lamb loin dry, sear hard on all sides, then roast in the oven with garlic and thyme until the core temperature reaches 56 °C (133 °F), and rest before slicing.
Why this lamb loin fits keto well
Lamb loin provides about 22 g of protein and 18 g of fat per 100 g of raw meat, a very balanced profile for keto. 250 g of lamb loin per serving yields roughly 50 g of protein and 40 g of fat from the meat alone. The garlic-thyme butter (15 g per serving) adds another 12 g of fat. Garlic in moderate amounts (3 cloves per 500 g of meat, so about 1.5 cloves per serving) brings around 1 g of net carbs; fresh thyme and rosemary are nutritionally negligible. Olive oil for searing rounds out the fat. In total, a serving lands at around 2 g of net carbs, 50 g of fat and 54 g of protein at about 650 kcal, a classic high-fat, high-protein profile for keto.
Source: USDA FoodData Central, Lamb, loin, raw , NIH Office of Dietary Supplements, Thiamin (lamb is a notable source)
Lamb loin internal temperature: rare, medium, well done
Lamb loin is a lean prime cut and should not be cooked through. Target temperatures: 52 to 54 °C (126 to 129 °F) for rare (deep pink inside), 56 to 58 °C (133 to 136 °F) for medium-rare (light pink, juicy) and 60 to 62 °C (140 to 144 °F) for medium (slightly pink). Above 65 °C (149 °F) the meat turns tough and dry. Measure with an instant-read thermometer, since the lamb loin has uneven thickness; always probe the thickest spot.
How much garlic fits into keto?
Garlic contains about 28 g of net carbs per 100 g, which sounds like a lot, but a single clove weighs only 3 to 4 g, so it brings only about 1 g of carbs. 1.5 cloves per serving is no problem within a ketogenic daily budget. If you tolerate garlic especially well and want to use more, roast the cloves alongside the meat (whole cloves confit in the oven turn mild and sweet, without adding noticeably more carbs than raw cloves would).
How to serve and vary the lamb loin
After resting, slice the lamb loin across the grain into 1 cm (about 3/8 inch) thick pieces and pour the garlic butter from the pan over the top. From experience, it pays to collect the pan drippings and serve them separately as a jus, they hold all the flavor and act as a natural sauce for the lamb.
Meal prep: making ahead and reheating
Lamb loin is best eaten fresh, since reheating quickly turns it tough. If you do end up with leftovers: add cold slices to a salad bowl or warm them briefly at 70 °C (160 °F) in the oven (not the microwave). The garlic butter keeps for 5 days in the fridge and can be used on its own for other dishes.
If you do not want to use the oven
Instead of the oven, the lamb loin can be cooked entirely in the pan: after searing, reduce the heat, baste with butter and garlic, and cook over medium heat for another 6 to 8 minutes. Check with a thermometer for a 56 °C (133 °F) core temperature. This works for 1 or 2 small pieces; larger pieces cook unevenly.
Which tips help with keto lamb loin from the oven?
- Take the lamb loin out of the fridge 30 minutes before searing; room temperature ensures even cooking.
- The pan must be smoking hot, otherwise there is no Maillard reaction and no crust.
- Lightly crush the garlic cloves (do not chop them) so they will not burn in the pan.
- Use an instant-read thermometer, aim for 56 °C (133 °F); the lamb loin will rise another 2 to 3 °C during resting.
- Let it rest for at least 5 minutes, otherwise the juices will run out when slicing.
Nutrition values
| Nutrient | Per 100 g | Per serving | Keto context |
|---|---|---|---|
| Calories | approx. 260 kcal | approx. 650 kcal | Full main course; energy mostly from lamb fat and butter. |
| Full main course; energy mostly from lamb fat and butter. | |||
| Fat | approx. 20 g | approx. 50 g | Saturated and monounsaturated fatty acids, an ideal ketogenic profile. |
| Saturated and monounsaturated fatty acids, an ideal ketogenic profile. | |||
| Net carbs | approx. 0.8 g | approx. 2 g | Very low; comes almost entirely from garlic. |
| Very low; comes almost entirely from garlic. | |||
| Sugar | approx. 0.3 g | approx. 0.8 g | Traces from garlic. |
| Traces from garlic. | |||
| Protein | approx. 22 g | approx. 54 g | Very high; covers about 36 % of the recommended daily protein intake for a 75 kg (165 lb) adult. |
| Very high; covers about 36 % of the recommended daily protein intake for a 75 kg (165 lb) adult. | |||
| Salt | approx. 0.4 g | approx. 1 g | Moderate; salted butter and seasoning salt, taste at the end. |
| Moderate; salted butter and seasoning salt, taste at the end. | |||
Note: Nutrition values are estimated averages per 100 g and per serving and may vary depending on ingredients, brands, portion size, and preparation. They do not replace individual nutrition or medical advice.
FAQ
What is the difference between lamb loin and rack of lamb?
Lamb loin (also called lamb backstrap) is the deboned loin, a cylindrical fillet cut. Rack of lamb is the same loin with the rib bones still attached; individual lamb chops are cut from it. Both have similar macros (around 22 g of protein and 18 to 21 g of fat per 100 g). Lamb loin is easier to portion, while rack of lamb looks more elegant on the plate.
How long does the lamb loin need in the oven?
For 500 g of lamb loin at 180 °C (355 °F) fan: 15 minutes for rare (52 °C / 126 °F), 18 minutes for medium-rare (56 °C / 133 °F), 22 minutes for medium (60 °C / 140 °F). For thicker pieces (over 4 cm / 1.5 inch in diameter), add 3 to 5 minutes. Always check with a thermometer; cooking times are only guidelines.
Do I need to marinate the lamb loin first?
Not necessarily, fresh lamb loin has plenty of flavor on its own. A marinade of olive oil, garlic, rosemary and thyme (overnight) will deepen the flavor further. Acidic marinades with lemon juice or vinegar should sit for no more than 2 hours, otherwise the protein on the surface denatures and turns mealy.
Does this dish work for losing weight on keto?
Yes, 54 g of protein keeps you full for a long time, and the low carb count (2 g) leaves plenty of room in the daily budget. To trim calories, reduce the butter to 10 g and skip the olive oil, since the lamb fat provides enough cooking fat; the serving then drops to about 540 kcal while still delivering 52 g of protein.